"Frode Berg" wrote

Can we shorten the life of the engine by letting the plane sit in the
hangar for many days/weeks between flights?

YES!!! That is the one factor that contributes most to shortened
engine life. Particularly during the initial break-in period if
one is using a "straight" mineral oil to facilitate the break-in.
The "straight" mineral oil, while promoting a faster break-in, also
drains off the camshaft lobes between flights more readily than does
a multi-viscosity oil with all of the additives. Several years back,
the situation was so bad with one particular engine, the Lyc O320 "H"
model, that the FAA required a special additive to be added to the
oil used in that engine to help the oil stick to the cam lobes between
flights. The additive was so sucessful that it is now a standard part
of the Aero Shell 15-50 oil sold here in the U.S.. At Sun-n-Fun a couple
of weeks ago, I saw vendors selling the additive alone. It wasn't
cheap, but compared to the price of an engine, it is well worth the
money.

The best advice....during the break-in period, use straight 50W mineral
oil and fly daily if possible and when the piston rings have seated and
oil consumption has stabilized, switch to a 15-50W detergent oil with
all of the additives.

Bob Moore
ATP CFI