You must be registered for see images
so from this image it can be seen that when the 5 kage found out that "madara" had hashirama cells, they believed that this was why he lived so long. they werent at all surprised by how young he looked. so i believe this is proof that hashirama didnt age because his life force was so great.
not to mention that thats why his cells were able to keep the real madara alive when he wouldve been dead. it is literally impossible for hashirama to die of old age.
also the fact that hashirama knew tsunade means that he lived at least thirty years after the final battle. the final battle happened 80 years before the current happenings, and tsunade is only 50.