Not at all........................assuming that the engine is in good operating condition. Also depends on the type of driving done over those miles. I would rather buy a car with over 100K highway miles than one with only 40K of only city driving. The easiest thing you can do to an engine is get up to highway speeds and just cruise, an engine will last almost forever when held to a constant load and rpm.
Boost is the only way to go. The added pressure might reveal a weakness that currently exists in your stock setup, but that just means a rebuild with forged components and MORE boost.
If you're truly concerned, do a leak down test. They can be useful in determining the present health of your motor.
Anyway, I wouldn't let mileage stop me. Boost it and enjoy it till it stops... I had 2.5K on mine when I put my KB on it and presently has 24K and have never had a problem and I've had loads of fun!