I prefer this too. My 3 options are:
1 - Make Bruce getting normaly older for other caracters getting older, the is Batman Beyond but without Bat Boys
2 - Make Bruce des-age with magic/cience and he will keep before 40's for much more time while Damian and other Batboys can get 10-15 years older.
3 - The paralelal publication when everybody can get older as I said before.
*Jason is immortal now? I think I read this in like "10 things you don't know about Red Hood" but haven't see this in a real comic page.