hard question to answer becuase im not consistent either. For example the last few months its been a couple a month, prior to that one month it might be 1 a month others a few.
Being a PC gamer gives me the advantage of sales. Last year during the Christmas sales I think i purchased about 30-40 games within a month and spent maybe $100-$150. Then i spend the next 6 months playing some of them.... I still havent got through them all.
Games for me are a bit like a collectors hobby thing. I like the idea of having a shelves full of games which is why i always prefer box over digital download. Plus I like the idea that i can gift them to my nephews or lend them out to friends to play.
tldr; i put every 2 weeks but it changes depending on the season