I’ve not used Decky before, it always seemed like one of those things that needed constant tinkering. Is it still a bit bleeding edge or has it reached the “it just works” stage yet?
As others have said, the best answer is “whenever you want”, though obviously sometimes you don’t know when that is! If you need a little more structure you can see what the game presents to you as all the things you can do, for instance by completing all the achievements. Remember that sometimes the final achievements are ludicrously difficult, so if you’re not enjoying it just call it a day!