I don't do this with games. Ever. Never had a single cart or disc fail on me.
However I do own many duplicate consoles. Considering consoles fail far more often than old carts, I tend to like having spares around. Also, I modify a LOT of them
I don't typically buy to resell though, unless I'm buying specifically for the business. I also tend towards broken or beat up consoles as dupes. I've really started to enjoy reconditioning and restoring older systems in the last year or so, and I find that I spend most of my game-related free time doing so.