It depends how often you want to buy new games. I regularly consume gaming media for fun, so often I only need to watch a review or two to get a solid idea of if it's worth a purchase, so maybe 10-20 minutes, and often times you can just listen to the review in the background of doing other stuff. And I only need to do that maybe once or twice a month at the absolute most, I'm not super rich or anything.
This is all implying I already have good trusted review sources. I'd recommend ACG Gaming if you don't know any yet, he's a smart writer and goes very in depth in his reviews. He buys all of the games he reviews for integrity purposes.
Of course, if you're being absolutely honest that you always buy a game you like after pirating to try it, I think that's just fine, I have no qualms about using piracy as a tool that way, this is just how I do it.