There's a reason the Quick Start guide starts with a stability warning 🙂

The standard in larger game studios using other engines like Unity, Unreal Engine, etc. is to pick a version and stick with it for the development of a game, not to spend a ton of time and resources constantly porting to newer versions. The same can be done with Bevy; you don't have to update unless you want to. Though, of course, because it is still evolving so rapidly, each version often adds things that may be very useful for your project, and learning resources can get outdated, so there is incentive to update. Whereas with more mature engines, there are typically enough features that there is less need to use the latest version.

Personally my experience (~3-4 years, though primarily as a library author) with Bevy updates has been that migrations really aren't too bad, typically taking 20 minutes to a couple hours to get things to compile and work like normal, and maybe some more to adopt any new features or APIs. The most painful part of migrations is waiting on ecosystem crates to update, but that is a bit better nowadays with the RC process, and oftentimes you can also update smaller crates yourself, if needed. Also, if you rely on advanced rendering internals, those can break in hard-to-debug ways.

But yeah, it's totally reasonable to use something more mature and stable; like the Quick Start guide says, Bevy is still in fairly early stages of development (game engines are big), and things break and evolve often :) I would expect stabilization to happen gradually, with core parts like the ECS having fewer large breaking changes over time. But no engine is ever finished unless it is abandoned, even engines like Unity, Godot, and Unreal Engine still have breaking changes.