The 172s develop cracks in the stabilizer spar, 150s develop cracks in
the fin attach fittings, and the anchor nuts for those bolts will
crack. 150s also develop enough wear in the rudder hinges that the
rudder stops will go past the stop bolts and jam the rudder hard over,
killing all on board. There's an AD on this, as well as the fin anchor
nut propblem.
Cessna has numerous service bulletins on various age-related
issues on their airplanes, and my experience has been that most folks
ignore them, since they're not "mandatory" like an AD. The cracking
stab spar fits into that one, and almost any 172 with 5000 hours on it
will have that cracking. Many folks move their airplanes by pushing
down on the stab to turn it; Cessna has determined that this will
crack that stab spar much sooner. We don't let our instructors and
students do it. It also deforms the nose rib at the stab root. If any
pilot saw how light the structure is in there, he'd never touch that
stab again. The forces involved in lifting the nose by puching on the
stab are much higher than those in normal flight, since the main
wheels are well behind the aerodynamic centre of pressure.
Cessna has a Continuing Airworthiness Program that we also follow,
and things like engine mount crack inspection at 10,000 hours and
every 2000 thereafter is listed; we've found cracks at 7000 hours, and
at 10,000 we found five more. The wing spar roots and carrythoughs are
to be eddy-current tested at 12,000 hours. We're not there yet but I
wouldn't be surprised if we find some small cracks.
If you can't find evidence in the logs that the mechanic has
been paying attention at least to ADs and SBs, you can expect some
expensive repairs.

Dan