A fair point well made.
Works both ways really.
Overly enthusiastic leaning will as you say add to engine wear and reduce life, although properly done leaning shouldn't (especially in an aircraft actually fitted with an EGT gauge).
On the other hand routine red-lining of the throttle to cut 5 minutes off journey time, taking off as soon as possible (because it's on the tacho) rather than idling to warm the engine up properly for a few more minutes, or shutting down the engine immediately the aircraft is parked, rather than again letting it idle for a few minutes and settling down. All those things reduce the engine life.
I suppose ultimately wet-leasing is much easier on the paperwork.
G