You guys are obsessing about durability and longevity of a finish on beds that aren't going to be used for serious hauling, are never going to sit out in the rain, and won't even see the sun all that much.
You could put a slap dash paint job on the bed wood and it will still outlive all of you. POR-15 with a topcoat is overkill for no real benefit.
Prime it and paint it with a good oil base porch paint and you'll never have to worry about it for the rest of your life.
