This obviously depends on what condition you prefer. some may see maggot filled pussy as a benefit. LOL
you could preserve body to last forever by soaking it with formaldehyde but if you try to fuck it you will soon follow the same fate.
But I think the better solution would be to get employed somewhere where they provide you the supply of fresh corpses.
Plastify it like they do for the BodyWorlds exhibit. You'll be able to fuck it as long as you want, as long as you're careful and don't mind it being an unyielding solid block.