Average lifespan of a business jet?

One other major item that you need to do with whatever you decide to
purchase is to take the time run down the list of recommended and
required inspection or overhaul items due within the next couple of
thousand hours and get a handle on the costs of them. You don't want
to drop a bunch on an jet that turns up needing a required inspection
or overhaul that rivals the purchase price.

I had an aquaitenence that bought a jet for a fantastic price, but
ended up grounding it 300 hours later when a mandatory inspection came
due....the labor cost exceeded what he paid for the jet. He though it
was a very simple inspection, but it wasn't and it really bit him in
the butt when got the estimate.