As mentioned surely the plane has had it engines changed out several times. But the engines which started in one F-15 way back (well F-15A's built back in mid 70's are becoming rare, though most are still relatively old) might still be in another now. They've been overhauled and rebuilt replacing wearing or fatigue life parts, but P&W hasn't built several complete fleets worth of completely new F100 engines for F-15's i in the last 30 years. You might say the engines are kind of like your grandpa's old hammer where your dad replaced the handle and you repaced the head , though not quite, some parts neither physically wear nor come under much stress in operation.With regards to a modern airforce, I don't think an F-15 sitting on the apron at Holloman AFB in 2010 has the same engines it rolled out of Long Beach with in 1974. I don't know that for certain but it doesn't sound feasible so the statement 'engines have to last because that's how long the plane lasts' feels limited in accuracy to me.
But TBO's for fighter engines, which is really what we're talking about, the Me262 engines wouldn't necessarily be completely sh*tcanned either I wouldn't guess, have multiplied if anything more than the lives of the a/c themselves, especially if you compare on an apples to apples basis their lives in peacetime service. Though, the fact that a WWII combat a/c would likely be destroyed in a weeks or months in a combat zone, or else become obsolete not long after that, or simply wear out itself (for example Soviet fighters with wooden and fabric parts) was a factor in considering equipment life, obviously. Perhaps it should have been in more cases (as in criticism of US Browning .50 of being a long lived machine gun heavy for its performance compared to shorter lived Soviet 12.7mm a/c mgs). But late war German jet and some piston, engines had short enough TBO-lives to cause servicibility/availability problems with the planes they were fitted in.
Joe