The 5yrs is somthing that been around for decades.
It to do with liability for sure.
That said if you were wearing it 12 hrs a day 7 days a week for 5yrs. There is a good chance that it should be replaced.
That said there are 1000,s of soldier in Canada wearing armour that's 10 years +old
Almost evey correction officer I have talked to right now has expired armour.
Back say 20 years ago delamination of hard armour due to exposure to UV was a thing.
But NIJ.06 pit onto place things that would reduce that.
As well as epoxy resin that hold the plates today is so strong it has a half life of 100 years.
If it's for personal use and or as a grap and go armour for a police officer.
The plates will be obsolete way before they become un useable.