How long do the backup batteries in NES games last?

I recently found my copy of Dragon Warrior in the original box! I remember I had Erdrick's level maxed out (had a lot of time on my hands back then) and defeated the dragonlord with only the bamboo pole equipped as my weapon.

Would the game still be saved? I'm thinking that the battery died long ago.

I believe you have like a year left or something, maybe 2 years, I just fixed all my super nintendo cartridges were the battery died, and they died like months ago. If you need batteries, go to http://www.racketboy.com/retro/2006/11/how-to-change-snes-game-save-battery.html.

Might want to check which battery it is first though.

you're totally still gonna lose that save file even if you change the battery... that's the one downside i can think of when thinking about changing batteries. and yeah, it is pretty simple.

Sorta related, but my sega genesis copy of Sonic 3, form the day it was released in like 1992/93 Can't remember, still works today :DJigglyWiggly_

Thanks everyone. Will have to find an old NES to fire it up to see.

im not sure, it seems to be up to the individual game.

ive heardthatmany Pokemon Goldcarts for Gameboy cant save anymore, and yet Pokemon Red seems to mostly still work.

it really depends on the game and whos making it, probably to do with the quality of the battery