I’m currently using Anki version 25.07.5. Should I update to the latest version, or is it safe to keep using 25.07.5 indefinitely without any significant risks or issues?
Use it. Nothing will affect you. Unless, of course, you’re using new versions of add-ons. I don’t have time to check older versions, and I can only check 25.09 and that’s it. And version 26.08.1 is more stable for me than all the others this year.
For what its worth, 25.09.3 and 25.09.4 were security updates, so you might want to upgrade at least that far.
The most significant changes are the new installer (26.05) and the (very) experimental editor (26.08). Most reports we got are related to that (in addition to usual graphics issues caused by Qt upgrades). Add-on compatibility issues should be minimal.
There are a lot of bug fixes though - check the release notes to find if something is relevant for you: Releases · ankitects/anki · GitHub