It seems to be simple mathematics. It is only a question of "when" you will buy the new battery. You can either buy it now with the truck or later when the used one craps out. My suggestion is to buy the truck with the used battery. Any amount of time that it lasts is a bonus because at some point you will need to replace it...and right now the price of batteries is through the roof and are fictitously high because of speculators in the market.