depends. he grows older with more experience, but at the same time, he might considered OLD, as we don't know how long he's going to live. maybe he only a had a few more years to live. if so, he would be weaker. but if he had about a hundred more years to live, he coulda super super strong. maybe gain some more limit breaks, discover new materia... it's up to fanfiction writers for this one haha.