@425RuS Sorry you didn't get a response sooner; your post was just moved to the Sims 3 section this morning.
Try deleting your options.ini file (if you've set your OS to hide extensions, it may just show as options) inside your TS3 game folder in Documents. When you launch the game again, a new copy of the file will spawn, and hopefully you'll be able to change your sims' lifespan. You'll need to redo your other settings as well. Keep in mind that while most settings are adjustable at the Main Menu, lifespan settings can only be changed in-game.
If this doesn't help, is it possible that you have a mod that's governing or interfering with your settings? You can list any you've installed, except for the few that raise the game's rating from teen to mature.