Not necessarily. It's really dependent on a lot of factors. Quality of work/parts/tuning, types of mods, regular maintenance, and most importantly how you drive the car. My WRX has over 100,000 miles on it, 80,000 of those miles with 65% more HP than stock and all I've had to do is regular maintenance (::knockonwood:
. I've seen a lot of stock engines explode with less miles than my wagon.
Also, the turbo Subaru engines are WAY more bulletproof than their n/a motors. A Subaru tech always tells me how crazy it is to see so many more n/a cars come in with bad engines than the turbo engines.