I've been stockpiling them ever since the Canadian dollar prices were going up for video games, a little after the PS4 went from $399 to $449 around March/April 2014. So with all the cards I have, I think I'm good until maybe 2021.
I'm also guessing that if there are any 'discounts' on Canadian Black Friday, they'll knock $20 off the price and put them on sale at $49.99 again. That's what they usually do with their controllers.