They were affected by the turning of the Wheel, being trapped too close to the surface of the Bore, and were described as being impossibly aged.

Of course, one could reason that it is the very channeling of the OP that keeps Aes Sedai young and fresh, and that neither of these two experienced more actual time than their original 600 year lifespan could have handled. In fact, Aginor even started to look healthier as he channeled. But IMO, this doesn't hold up. If it was the act of channeling itself that kept AoL folks alive, I say Aginor and Balthamel would have died within the Bore. But they didn't, as their faustian deal prevented time from killing them.

Funny as the sequence with those two always reminded me of the Picture of Dorian Gray for some reason...

I say it is far more likely, given the evidence we have, that the DO's touch has somehow frozen the Forsaken in time. Whether by tying off their life threads or setting them aside from the pattern altogether, I don't know. If I had to guess, I'd say time is related to whichever deity is turning the Wheel at the present time, and that the bonds to the DO "holds the Forsaken back" as the Wheel turns.