My grandpa had 7 siblings. The oldest is about 25 years older than the youngest. Mom's youngest Aunt is only a couple years older than she was and they were raised more like cousins or sisters. The oldest... were not.
So yeah, for Aunt may to be a doddering old senior citizen is entirely legitimate. She COULD be younger... but frankly that's a retcon I don't care for. She was created to be the grandmotherly old woman that Peter felt the need to take care of. Turning into someone in her 40's and dating Tony Stark or whatever is basically a completely different character.
Keeping a character that the creators made... but changing EVERYTHING about them kind of misses the point of keeping the characters around.