I am different. At least with DRM-free games (like GOG), I narrow it down to:

- Would I want to play this at some point of my life?
- Even if I don't necessarily want to play it through, is there some other reason I want to have it, like being a piece of gaming history (e.g. Ultima 1)?

If yes to either question, then I will most probably buy it, at least if it is in sale. For games with DRM, the list is similar as yours, ie. I most probably won't buy a game until I really want to play it in the near future, and/or it is in a deep sale that doesn't necessarily occur that often.

The thing is with DRM-free games, I also consider what happens if the game disappears from stores, for good. Then I'll be kicking myself in the head for not having bought it earlier, if it is a game that interests me. How many times have we had those threads where GOG announces a removal of a game, and lots of people are rushing to buy the game, or complaining why GOG didn't warn about it earlier, or arrange a farewell sale for the game?

Yes, in many such cases I've felt "phew, I'm glad I've already bought the game".

Don't buy it if you don't want to play it a lot in the next couple of weeks. Later it will be probably cheaper anyway. And maybe you wouldn't even play it, then it is a waste of money.