Are engines at work get roll ins done about ones a year.There is very little and talking little sludge in the oil pan.This is because the
oil now days is very clean.
Also there is same amount of sludge in the pan hot or cold. The hot thing is to get you to change the oil as soon as it comes in.So the company
can get more done.Good ploy.
Dropping oil pans for 30 years I have seen the changes in oil first hand.
If the maintenance is done a the proper schedule the viscosity of the oil is still high, holding most contamination suspended.