I bought a used 120 gallon tank at auction, took it home and put a few gallons of fuel in it, found a tiny leak from wear in the bed of a pickup. So I then drained the tank and cleaned the area real good, applied JB weld to the leak, let it cure for a few days and I am still using the tank for storage. No problems.
This has been several years ago, and I just leave the tank on a stand, not bouncing around in a pickup box to do more damage to the bottom of the tank. I also use a good filter mounted just downstream from the pump. I also use about 75 to 100 gallons a year, so the fuel stays "fairly" fresh.