You may not agree, and maybe your mechanic doesn't agree ... but as said
in an earlier post, if you think about all the airplanes in flight
schools that are doing simulated engine failures far more frequently
than we would (some much more powerful than an 0-320 ... I can't
remember what engine you have), there would be many more engine problems
in rental/school airplanes than there are if there's nothing worse for
an engine than simulated engine-outs.

My mechanic -- a guy with over 40 years of experience as an IA, A&P,
grand champion home builder, and owner of an engine and prop shop --
says it this way:

The average privately owned GA aircraft is flown AT MOST once a week.
As a result, rust (from inactivity) is the #1 killer of the average,
privately owned GA engine. Many don't make TBO because of
inactivity.

Touch & goes are the #1 worst thing you can do to your engine. Flight
school planes do them all day long, but it's because they are flown
daily, sometimes 8 hours per day, and they therefore NEVER experience
the ravages of inactivity. Therefore, although it's STILL the worst
thing you can do, the engines often make it to TBO simply because they
are flown all day, every day.

Engine out practice is essentially the same engine management
procedure as a touch & go. Long periods of high power, followed by
suddenly low RPM, followed by a sudden application of power at the
end. Bad, bad, bad.

Are the engines designed to take this kind of abuse? Sure. But they
were designed to be run daily, not weekly, too. And when you are
paying something in the range of $20,000 for an overhaul (as we did
for our O-540) we don't generally make a practice of stressing the
engine any more than necessary.
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"