I wish I knew the exact answer to your questions.
It is my understanding that every warranty customer gets a survey, with some exceptions.
1 - Have they been in recently (don't know the definition of recently) and already received one.
2 - Some recalls are not surveyed.
3 - So far we haven't seen a customer with free service get a survey on the free service.
4 - Basically if you screw-up in any way - OR IF THE CUSTOMER ***THINKS*** YOU SCREWED UP - that customer is sure to get a survey and always return it.
IMHO
How many people in this world are "completely satisfied" with anything or anyone. If everyone was completely satisfied we would all be perfect with no room for improvement. I don't know about you but I have a long, long way to go just to get to satisfaction. That may happen about the same time I retire. Not sure, but the older I get the more it looks like it will happen about the same time.