...can anyone provide representative numbers for the modern engines as to how long they typically operate before being removed?
Today's issue of AW&ST (p.46) states "The GE90 is is now averaging 3,200 cycles before requiring maintenance--the equivalent of 20,000 hr. on wing" per GE.
Operating cycles -- startup, TO, climb, cruise, descent/landing, R/T -- are a better measure of wear & tear than sheer flight hours. The longhaul operator will obviously accumulate more hours.
A long time ago the DC-3 operator I worked for had a devil of a time getting R-1820's to run 1200 hrs!