Aye, you really should. To my knowledge those old cartridge based games have battery-fed memory for save files. It's 2012 now, those batteries aren't going to hold out for much longer, particularly for the older systems.
It's been a few years since I've had them out. Not that long, but I do check them every so often. Last time I had them out, all the cart-based games worked. Even Legend of Zelda (NES) still had my first file on it where I beat the game the first time. Never saved over it. Same with Link to the Past (SNES).
If they ever were lost or corrupted, I'd be a little bummed, but I know stuff like that can't last forever, what with the batteries being so old.
Good thing that happened today: I got a haircut. I am much cooler. If just literally instead of also figuratively.