On a serviceable aircraft, you must run the engine for 5 minutes at ground idle every 7 days, as per the Maintenance Manual 71-05-01-530-801-A01.
If you don't want to run it up, carry out the internal corrosion as per the Maintenance Manual chapter 71-06-01-620-801-A01, and motor the engine over for 15 seconds, 3 times, every month.
It's been there for a few years now.