Lord Parashurama believed to be one of the Avatars of God Vishnu. I have seen that Parashuram were present in Ramayana (When God Ram breaks the God Shiva's blessed Bow to marry Goddess Sita) as well as in Mahabharatha (as a teacher who teaches secret and deadliest arts of battle to Bheeshma). As far as I know, these two epic stories were happened in completely different Yugas.
So, how was Lord Parashurama alive so long? Or is he immortal?