diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index d9b9031..b6bafa4 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -49,9 +49,6 @@ jobs:
         - build: win-msvc
           os: windows-latest
           rust: stable
-        - build: win-gnu
-          os: windows-latest
-          rust: stable-x86_64-gnu
     steps:
     - name: Checkout repository
       uses: actions/checkout@v4
@@ -64,9 +61,31 @@ jobs:
     - run: cargo test --verbose --all
     - run: cargo test --verbose -p jiff-cli
     # Skip on Windows because it takes freaking forever.
-    - if: matrix.build != 'win-msvc' && matrix.build != 'win-gnu'
+    - if: matrix.build != 'win-msvc'
+      run: cargo test --verbose --lib --profile testrelease
+    - if: matrix.build != 'win-msvc'
+      run: cargo test --verbose --test integration --profile testrelease
+    - if: matrix.build != 'win-msvc'
       run: ./test
 
+  # Tests for stable-x86_64-gnu. It's different enough from the "main" targets
+  # to warrant its own section. The main problem is that it is just
+  # annoyingly slow. Like, twice as slow as the next slowest runner. So we
+  # run a stripped down version of tests.
+  win-gnu:
+    runs-on: windows-latest
+    steps:
+    - name: Checkout repository
+      uses: actions/checkout@v4
+    - name: Install Rust
+      uses: dtolnay/rust-toolchain@master
+      with:
+        toolchain: stable-x86_64-gnu
+    - run: cargo build --verbose
+    - run: cargo doc --verbose
+    - run: cargo test --verbose --lib
+    - run: cargo test --verbose --test integration
+
   # This job runs a stripped down version of CI to test the MSRV. The specific
   # reason for doing this is that Jiff dev-dependencies tend to evolve more
   # quickly. Or if I want to use newer features in doc examples. There isn't as
diff --git a/Cargo.toml b/Cargo.toml
index 8e7fefa..204a07a 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -120,9 +120,13 @@ version = "3.9.0"
 path = "tests/lib.rs"
 name = "integration"
 
-[profile.test]
-opt-level = 3
-
+# This is just like the default 'test' profile, but debug_assertions are
+# disabled. This is important to cover for Jiff because we do a lot of extra
+# work in our internal ranged integer types when debug_assertions are enabled.
+# It also makes types fatter. It's very useful for catching overflow bugs.
+# But since there's a fair bit of logic there, it's also worth running tests
+# without debug_assertions enabled to exercise the *actual* code paths used
+# in production.
 [profile.testrelease]
 inherits = "test"
 debug-assertions = false
diff --git a/src/civil/date.rs b/src/civil/date.rs
index f1b8590..79d84fc 100644
--- a/src/civil/date.rs
+++ b/src/civil/date.rs
@@ -3606,7 +3606,7 @@ mod tests {
 
     #[test]
     fn all_days_to_date_roundtrip() {
-        for rd in UnixEpochDays::MIN_REPR..=UnixEpochDays::MAX_REPR {
+        for rd in -100_000..=100_000 {
             let rd = UnixEpochDays::new(rd).unwrap();
             let date = Date::from_unix_epoch_days(rd);
             let got = date.to_unix_epoch_days();
@@ -3618,7 +3618,8 @@ mod tests {
     fn all_date_to_days_roundtrip() {
         use crate::util::common::days_in_month;
 
-        for year in Year::MIN_REPR..=Year::MAX_REPR {
+        let year_range = 2000..=2500;
+        for year in year_range {
             let year = Year::new(year).unwrap();
             for month in Month::MIN_REPR..=Month::MAX_REPR {
                 let month = Month::new(month).unwrap();
@@ -3636,22 +3637,12 @@ mod tests {
     fn all_date_to_iso_week_date_roundtrip() {
         use crate::util::common::days_in_month;
 
-        // This test is slow enough in debug mode to be worth tweaking a bit.
-        // We still want to run it so that we benefit from ranged integer
-        // checks, but we just do it for ~1000 years. We do it for at least 400
-        // years to capture a single Gregorian cycle, and we also include the
-        // upper boundary of years because there is some special cased logic
-        // for dealing with that specific boundary condition.
-        let year_range = if cfg!(debug_assertions) {
-            9000..=9999
-        } else {
-            Year::MIN_REPR..=Year::MAX_REPR
-        };
+        let year_range = 2000..=2500;
         for year in year_range {
             let year = Year::new(year).unwrap();
-            for month in Month::MIN_REPR..=Month::MAX_REPR {
+            for month in [1, 2, 4] {
                 let month = Month::new(month).unwrap();
-                for day in 1..=days_in_month(year, month).get() {
+                for day in 20..=days_in_month(year, month).get() {
                     let date = Date::constant(year.get(), month.get(), day);
                     let wd = date.to_iso_week_date();
                     let got = wd.to_date();
diff --git a/src/timestamp.rs b/src/timestamp.rs
index a0dbb69..5d13ec7 100644
--- a/src/timestamp.rs
+++ b/src/timestamp.rs
@@ -3057,7 +3057,7 @@ mod tests {
     }
 
     #[test]
-    fn to_datetime_every_second_in_some_days() {
+    fn to_datetime_many_seconds_in_some_days() {
         let days = [
             i64::from(t::UnixEpochDays::MIN_REPR),
             -1000,
@@ -3066,12 +3066,15 @@ mod tests {
             2000,
             i64::from(t::UnixEpochDays::MAX_REPR),
         ];
+        let seconds = [
+            -86_400, -10, -9, -8, -7, -6, -5, -4, -3, -2, -1, 0, 1, 2, 3, 4,
+            5, 6, 7, 8, 9, 10, 86_400,
+        ];
         let nanos = [0, 1, 5, 999_999_999];
         for day in days {
             let midpoint = day * 86_400;
-            let start = midpoint - 86_400;
-            let end = midpoint + 86_400;
-            for second in start..=end {
+            for second in seconds {
+                let second = midpoint + second;
                 if !UnixSeconds::contains(second) {
                     continue;
                 }
diff --git a/src/tz/tzif.rs b/src/tz/tzif.rs
index f172b7a..8990e72 100644
--- a/src/tz/tzif.rs
+++ b/src/tz/tzif.rs
@@ -1478,8 +1478,8 @@ mod tests {
     }
 
     /// This tests walks the /usr/share/zoneinfo directory (if it exists) and
-    /// tries to parse an TZif formatted file it can find. We don't really do
-    /// much with it other than to ensure we don't panic or return an error.
+    /// tries to parse every TZif formatted file it can find. We don't really
+    /// do much with it other than to ensure we don't panic or return an error.
     /// That is, we check that we can parse each file, but not that we do so
     /// correctly.
     #[cfg(target_os = "linux")]
@@ -1492,6 +1492,12 @@ mod tests {
             // These aren't related to our parsing, so it's some other problem
             // (like the directory not existing).
             let Ok(dent) = result else { continue };
+            // This test can take some time in debug mode, so skip parsing
+            // some of the less frequently used TZif files.
+            let Some(name) = dent.path().to_str() else { continue };
+            if name.contains("right/") || name.contains("posix/") {
+                continue;
+            }
             // Again, skip if we can't read. Not my monkeys, not my circus.
             let Ok(bytes) = std::fs::read(dent.path()) else { continue };
             if !is_possibly_tzif(&bytes) {