I think the Gold and Silver cartridges died a few years ago. Already know my Gold game is dead and pretty sure Silver will be by now. Don't want to check on the others, rather believe they are still there. When Gold died I make a list of my 6 squad Pokemon on Blue and all their details so it could save as a reminder/memorial of sort. Reading this kinda glad I did it.
Despite nostalgia, I'm unlikely to ever pick them up again seeing as I have the DS version and haven't finished either HeartGold or White.
EDIT: In a few years time, will we be having to worry about this with Ruby and Sapphire and then all the DS games. I read somewhere the DS games' internal batteries work in a way that when they run out the save files remain but time-based events don't occur. Have I got that right?