Yes, keep it on flat surface. I do not think body armor "expires" unless exposed to elements and under constant use.. I keep mine on a flat surface in my bed room. I am interested in a vest for plate carriers but CBA to spend $400 a plate but then again that is a life time investment, just like buying two guns. In these times its not a bad idea. Esp if you are in a big city.
SHTF vs TEOTWAWKI you ask? SHTF, just some crap on the ceiling and walls, TEOTWAWKI end of the world as we know it. Orignally made by 9mm/®™©