Weekly cache expiry was behind recurring CI timeouts, not random flakiness

A development team repeatedly saw a CI linter job fail with a timeout error, only for it to pass when re-run, leading them to dismiss it as flaky behavior. Investigation revealed the job took 311 seconds against a 300-second budget — but only when the cache was cold after its seven-day expiry cycle. The second run passed quickly because it benefited from a freshly populated cache, masking the real problem rather than resolving it. This meant the build was silently failing once a week, every week, with the surrounding warm-cache days hiding the pattern. The fix was straightforward: raising the timeout limit from 5 to 15 minutes, with a comment documenting the root cause to prevent future teams from rediscovering the issue.