When is it time to replace a trailer?

i have a 99 all steel flatbed.. arch? what arch? can't really see one, but i've had 49k on it and it didn't sag enough to catch my attention.. paint is worn but it's a good thing in my book cause it allows me to see the steel beams that much easier and i have not stress or any other type of cracks.. only real issue is dented rub rails, and cracks on the welds of a couple of stake pockets.. but those cracks are an easy fix as soon as i get a hold of a arc welder.. got a single air leak and one ABA that doesn't auto adjust.. i just check it when i do my pre-trip and roll hard.. i think i messed up the auto adjust mechanism one afternoon doing a panic stop on I10.

the only reason i'd swap it out would be because it's too narrow, and heavy.. truck, trailer, gear, and full tanks i'm already at 33k.. i wanna try to knock that down to 31.5k if lucky.