As always, stable releases are about how frequently breaking changes are introduced. If breaking changes potentially happening every day is fine for you, you can use unstable. For many use-cases however, you want some agency over when exactly breaking changes are introduced as point releases a la NixOS provide you with a 1 month window to migrate for each release.
Is there a good reason to use point releases on NixOS? I always used unstable and the support is less than a year for releases anyways. It's a nice sprint to get all components in a polished state, but then again unstable hasn't really disappointed in that regard either.
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