Inspired by a three-year-old Kotaku article, Canadian blogger Rinry subjected eight NES carts to varying forms of torture to see just how durable the goods were. Seven of them were still fully playable.
This is a long, but very watchable (and well made) video. Plus you get to hear Rinry say "out" and it's always adorable when a Canadian says that word. Ultimately, the point is that old NES cart are rough-and-tough customers because the actual ROM boards comprise so little of them. You can do a lot of damage to the plastic, and so long as it still fits in the console, you're still good to go.
How Tough are NES Games? [Rinry Game Game, thanks Corey]