You bring up a very good point, in that a lot of medical issues are not recognized or diagnosed for many years after the fact. For whatever reason, some veterans manage to lead a perfectly functional life for many years, and then suddenly something happens that triggers something, and the next thing you know they've been diagnosed with PTSD. This could be 10 years down the road. I've seen it happen. It never happened to me, even though I was exposed to a lot of trauma while working in the Canadian Forces.
I've seen it happen personally with friends and other colleagues, but to place a time limit on it and labelling a veteran in that way I think is inappropriate.