A couple points from someone who has worn body armor pretty much every work day for the last 28 years.
Chances are, if you are not wearing it when things go down, you won't have time to put it on.
All the hard armor I have ever worn was when I was on SWAT for ten years, and, generally, it was on our time table. WE decided to run the warrant. WE decided to make entry. We had to respond to a barricaded person. The minute or so to throw on hard armor is trivial when it takes you 10 minutes to get there.
There is noting wrong with good folks having some armor around. But, buy good stuff if you are going to do it. If you think there may be an actual armed threat, it better be the FIRST thing you put on, because after the window shatters, or the front door is kicked, I'll bet you forget about it.
Hard armor is miserable to wear. Its heavy and, its hard to move, much less move quietly without banging into every corner.
For years, we did not wear helmets. The thoery was that is slowed down you movements and it was hard to "quick peek" around corners and windows. Helmet technology has come a long way. I would always wear a helmet now.
I was on SWAT for ten years, not anymore, but, I still have a set of plates in a carrier for an active shooter secenario. I always wear it through our two day active shooter schools just to remind myself how awkard it is to move around in it.
Most body armor has an experiation date. If it didn't, pencil pushers would keep cops in the same armor for a 25 year carreer. We too have shot old vests, they work fine. But, I would only be fairly sure about that with Kevlar. Some of the new materials can delaminate through heat and moisture. Two things my vest is constantly exposed to. I know there have been days in August here in Texas that every drop of cologne and deoderant I started with has soaked into my socks at the end of the day. That vest felt like I had jumped into a pool.