I have a leather seat and I haven't done a thing to it except maybe Lexol too infrequently to make a different. If it gets wet, it dries out -- I lived and rode I. Seattle rain or shine for years. Never had a problem. It's lasted 12 years, started cracking a little after 10. Actually, it's not even the leather that's failing...it's the stitching.
I'll get it recovered again in black leather, but this time I'm treating my ass to a gel pack.