No source I have read has suggested real world failure of expired body armor of any kind. In fact, all sources I have ever read reported performance on par with unexpired plates. The idea that AR500 steel will expire is laughable. It may rust if it’s uncoated, but if you add the spall coating to it there’s almost no chance of that. I know little about polyethylene but my hunch is that on year 5, day 1 it will still stop a bullet. Check out bulletproofme.com for some info on expired armor tests. YouTube also has a number of good videos.
Something else to consider is the weight of the armor. Steel plates are easily 8lbs or more each. With the necessary spall coating maybe more. A pair of those plates will run close to $200 if you don’t skinflint the process. Considering the price, ceramic level IV plates are a better investment. Again, they do not expire, and a pair will probably cost about $300-$350. They will be much more comfortable and are a better long term investment if you can swing the extra cost.
