De acordo com Melhores Práticas do OpenPGP em Riseup.net , sim, é possível, e parece não haver nenhuma recomendação contra isso:
People think that they don’t want their keys to expire, but you actually do. Why? Because you can always extend your expiration date, even after it has expired! This “expiration” is actually more of a safety valve or “dead-man switch” that will automatically trigger at some point. If you have access to the secret key material, you can untrigger it. The point is to setup something to disable your key in case you lose access to it (and have no revocation certificate).