I get the impression that these engines wear out quickly

[racer_d]

I think it the issue has a couple of prongs:

1) The tainting of the early cars having complete motor failure

2) Not many (especially original owner cars) have over 100,000 miles that we get to hear about. It seems that many Boxsters have gone through multiple owners even before 50K miles so getting examples of original owner cars with over 100,000 miles is hard to come by.

3) As you mentioned, it takes many Boxsters 10-15 years to hit that kind of mileage. These cars for many are 3rd car luxuries. Not daily drivers since day one. This isn't an indictment, just an opinion on who buys a Boxster nowadays.

I recall seemingly countless stories of both 914-4 and 911 (particularly 911SC owners) who logged 100-200K miles on stock motors without incident. At a time when "domestic" motors barely went 50K miles, this was unheard of, especially in a "performan car". Bulletproof is what many call the SC motor because of this legacy. Understressed and overbuilt. I don't think the 2.5 or 2.7 986 motors would be termed either understressed or overbuilt, but I don't see why properly maintained they won't go 100-200K miles before rebuilding. I am not sure how many people who own cars know what proper maintenance even means, let alone are willing to do it themselves or pay someone to do it right. This is especially true if one "dumps" the car after they get a nice expensive bill from their dealer.