Last time I checked (probably a few months ago), all my first/second gen games were still working. I bought Crystal on my birthday but didn't realize that the battery was dead until I played it a couple days later, and to my horror, the file didn't save. xD
I'm terrified of touching my Gold though. I don't wanna go through the horror of losing my save file. Shiny Rapidash, Shiny Crobat, the first Pokemon I ever raised to level 100 ... I don't wanna lose those. xD
Although I think the battery on my Gold IS dead but my file's still there, 'cause every time I turned the game on it had me reset the time and date.