I was thinking that since the curse resulted in Magus time travelling to 600 AD that the curse wouldn't be lifted until he died, but not like you were thinking so I'll try to explain (not very well though because I hve class very VERY soon so I'll try again later, please don't yell at me if this sucks).
Magus and Frog both travelled in time, in most scenarios they travel together. So they are now running on the same timeline. According to the Space-Time Continuum Theory, the events in Zeal are happening at the same time as the events in Truce, Proto Dome, Ioka, etc. So wouldn't this mean that Magus and Frog are kind of aging in the same way, as if they were still travelling together in time? If so then Frog would be very old if he was waiting for Magus to die even though he MAY be 12,600 younger than Magus.
I'm probably wrong, contradicted so many theories, and pissed a few people off really badly.