Obviously this is different for every person. For my part, I'm going to go w/ them for my first big tour. If I had a couple of buddies to go w/, it would be different. But I don't want to go solo for my first one. Note that the AC tours do have some flexibility:

1) the group members collectively make some choices about the itinerary
2) during the day you are on your own. usually the groups split into sub-groups of 2 or 3, but you can certainly spend the days by yourself when you want.
3) the tours also have a provision for people taking off for a few days on their own and rejoining the tour later. The leader has to ok any such diversion, and there are a limited total number of days anyone is supposed to be away (something like 10 for a six-week tour), but there is certainly some effort to give individual flexibility.

The big thing for me is to get out on the open road for a month, all my possessions on my back, self sufficient. Most importantly, I will not be in my office, not going to meetings, not humdrum day-to-day existence. I won't think about research or touch a computer (well, except my iphone) for the entire time.

I figure I have at least 20 more years to do solos.