Very interesting subject indeed? Here is a link I found on this subject yesterday : http://www.racketboy.com/retro/2006/11/how-to-change-snes-game-save-battery.html
I have a Super Mario Allstars cartridge that behave randomly. Sometimes, it would delete all my saves of SMB3. My GB Tetris cartridge won't keep my scores, and Pokemon Silver behave strangely as well. I might consider changing this Super Mario Allstars cartridge.
I also planned to buy a copy of Earthbound.
The problem is that Nintendo will never release games like Earthbound or Super Mario Allstars on the Virtual Console. And a VC release is the only solution, because soon or late, every poor little SNES cartridge will die if the battery is not changed.