When is a BUR considered bad?

I was in a meeting with a property manager explaining he needed a new roof due to seams on the cap were failing and blisters were everywhere, not to mention the 1 square of dry rot I had replaced last summer. Then a hot roofer tells him the roof should last another 2-4 years with no real problems. I didn't mention I have fixed 6-10 leaks on the roof this winter. So at what point is a roof considered bad?

In my mind when the seams begin failing the roof is at that important point where it is a candidate to be saved with a retrofit like glass emulsion, but waiting much longer will likely mean it has to be removed at much greater cost. The roof is at that "magic" point where the oils and saturants in the hot roof system can no longer accomodate the every day movement of the building with hot/cold day/night cycles. Cap it off now and save a bundle!

It's kinda like the tire on your car: if you have a nail in it and the pressure is low, if you deal with it now it can be made good as new with a $15 patch and more air. But ignore it for a few more miles anmd you'll find yourself stranded by the roadside and needing to spend $150 on a new tire.

When it leaks?