We did a 60-day caravan to Alaska this summer. We went with RV Adventure Treks
Tours to Alaska, Nova Scotia, Newfoundland and PEI. (Neal - please delete the reference/link if not allowed). I would recommend them, we had a great time. They are a small group caravan - 15 guest coaches plus a trek master and tail gunner. I think under certain circumstances they would accept up to a maximum of 17 guest coaches - I think that would primarily happen if a group of several friends wanted to sign up after the tour was already mostly filled. We went with 1 other couple that we already knew, but the rest of the group was unknown. The small group allowed everyone to get to know each other pretty quickly. Fortunately we had a great group. One of our fears was that we would get the group that had "that one guy". We thought about doing it on our own, but my wife was not keen on that. We researched all the trips to AK and RVAT spent the most days in AK from all the ones I could find with the exception of 1 company that was quite a bit more expensive. Our group was quite a mix, we had 1 pickup camper, 1 bumper pull, 1 class B, Three 5th wheels, and the remainder were Class A's - 2 gas and the rest DP's. Kind of surprising 8 of the Class A's were Newmars. We met in Dawson Creek, BC and finished in Prince George, BC. As for what happens if you break down - the tail gunner leaves 30-45 minutes after the last coach and watches to try to be sure they do not pass anyone. If they find someone broken down, they will stay with them for a given length of time. I forget the maximum time, but part of the rule was so the TG could still make it to camp by mid-late evening. If the coach was side of road repairable, they would stay while it was fixed. If it was not, they would assist in finding a tow. We had a couple of breakdowns, but they were both side of the road repairable.
Would I consider a caravan again? It depends - we like travelling by ourselves or with 1-2 friends, but we had a great time going this way. There was a lot to be said for having everything preplanned. We went to some things that I would not have picked if we went on our own. Some, I was pleasantly surprised. Others, my first thought was confirmed. I think most things in the CONUS we would be much more likely to do on our own (I'm sure there is an exception in there somewhere). Outside the US, we would most likely at least consider a caravan.