I just visited Winnebago service without an appointment the week before labor day. Their appointments were booked through October at the time. I got there on Monday at about 2PM. They allowed us to stay in their rally park across the street until they could "work us in" their schedule. They took my unit in on Thursday morning. But we didn't have to wait around all day or anything before that, I just checked in each morning and they said, check back tomorrow a couple of times, so we went off and did stuff during the day. Rally park had electric only at the site, but there were common dump stations and water faucets available - which I did use.
The service department kept two lists of folks waiting for repair work. One list of those with appointments and another of those without appointments. I was number 11 on the list of folks with no appointment when I got there on Monday. There were 12-14 appointment folks listed on the board at that time. They take you in order of arrival and squeeze you in their schedule, once they start work on your unit - they will continue to follow through to the end.
The form they had me fill out, as a non appointment person, allowed me to list 7 things that I wanted them to fix.