Engine lay up

At Kemble Flying Club we have a number of 80hp 912, two 100hp 912 and a 914 and, because of Coronavirus, I am being asked how long can we leave the engines before running them.  My experience tells me two or three months would not be a problem at all but is there an offical line on this?  I have also been advised it is a mistake to turn the props on a cold engine that is not going to be started as this can wipe oil off surfaces leaving them exposed, that does seem to make sense. I wonder if there are any contrary opinions?  Ref the 'experience' I have a rebuilt 912 spare engine that sat under a bench for two years and last year I had it opened up and checked and it was in pristine condition and that with no special protection just lubrication on assembly. dy