Steam game buying algorithm

Here's the algorithm I currently use for buying games on Steam. I am not a gamer and didn't even know about any of this until very recently.

1. Keep games you are interested in in your wishlist.
2. Don't buy a game that came out less than two years ago. (This is to generate enough historical pricing data in step 4.)
3. Never buy a game that isn't on sale.
4. When a game goes on sale, check https://steamdb.info/ to see if the current sale is good relative to previous sales.
5. If the game is on a good sale and is sufficiently interesting, buy it.
6. If I don't like the game or it doesn't work, return it (I think Steam allows returning any game for any reason if it has been played for fewer than 2 or so hours).