It make sense to what you are saying, as long as the same units are doing the job function every day and the service person is initmately knowledgeable of the various operations & hourly useage of each unit & is keeping records of when the "skipped' items are due; the PM frequency is in tune with the manufactures recommendation (most are backed on normal/clean and is kept in the communication loop when & if units are rotated to another job function/enviorment. As you well now, freezers units would need an increased frequency of PM as condensation & cold soaking plays havoc with everything on the units.
If you change service guys (girls) then you get to retrain again.