Ok, I guess that could have happened :). The movie made it look like he had aged normally and just wandered back when he got old since he didn't show back up via the "time machine".

Also there's the fact that they seemed to have discovered how to be immortal. When they were first experimenting with Ant Man he came back aged differently several times. Seems like you could just pop in when you were getting old, take off 20-40 years or whatever you felt like and come back again. But hey, this is comics and there's always a good excuse why you can't do something anymore. :)