The problem w/ springfield life time warranty is that they want the entire gun back....literally, lock stock and barell. That means you get to go by a hard case, a box to go over that, spend a bunch of time packing it up, risk loosing it to a dirty UPS employee, wait who know's how long for Springfield to finish, run the UPS gauntlet again. If you're lucky springfield will reimburse you for your shipping costs but none of the other stuff.
Its cheeper to just buy a new piston.