Seeing the wood floor, one thing you might keep a check on is humidity levels inside when it has been closed up for a while.
A company I worked for bought several containers to store used electrical equipment from job sites... Turns out the high humidity inside was causing significant corrosion damage to the equipment.
The problem: One of the containers being used also had a wooden floor and the bottom of the shipping container was not fully sealed off air tight with steel. With the unit sitting on the ground (on gravel under a metal shed), ground moisture was seeping up through the wood floor and causing very high humidity inside (to the point of condensing) on the walls and equipment.
We jacked the unit off the ground, placing concrete block underneath so air could circulate underneath the unit.. Helped a bit, but not enough to store anything valuable in it.