Those GBA games are Ambassador games, and as much of a pain it is to later adopters, Nintendo said they had no plans to offer them to everyone.
The batteries do die, but since the saves are saved on the cartridge's flash memory, you will never lose them. At least, my Sapphire is 10+ years and going strong despite having a dry battery
Wow, just read about that, who the fuck thought it was a good idea to cut off that possible revenue stream???
And great news about the Gen III saves, I'll have to look at eBay some more then!