Well it's not my trip yet, not with $1200 airfare for late November travel....but a trip I am thinking about in the event airfare comes down a bit.
I am thinking about experiencing a Christmas market blitz for 14 nights: Nordlingen, Dinkelsbuhl, Rothenburg, Heidelburg, Bamburg, Nurnberg, Regensburg. Might be open jaw between Frankfurt and Munich, staying in those cities the 1st and last night of my trip. So this means, spending 2 nights in the smaller cities. I know better than to have blitz-like travel when big cities are involved, but this is just to chill out and enjoy small town Germany, Christmas style. I have been to Rothenburg 2 times and still wish to stay 2 nights again. I have been to Nuremburg once but for 1 night only and didn't really get to soak the old town up. My questions are: Do Nordlingen and Dinkelsbuhl warrant a 2 night stay? Not counting Frankfurt and Munich (my fly into and out of cities which I do not care to spend more than a night in them), do Heidelberg, Bamberg and Regensberg warrant more than 2 days on a trip like this?
1) IMO, neither Nördlingen nor Dinkelsbuhl need more than one night's stay. They are both quite small and not far from one another - you could easily visit both in one day, in fact. 2) Heidelberg, Bamberg, and Regensburg are each interesting to visit, and i liked the Christmas markets in all three. Two nights is certainly sufficient for each. However, depending where your interests lie, you could fill a third day easily in any of the three, especially if you are traveling by car, and wished to include nearby areas as well.
I would add Idstein, Buedingen and Bad Homburg to your list of small towns to visit. These 3 have my favorite Christmas markets. The 1st 2 only have it for one weekend in Dec. Probably the 1st weekend. Bad Homburg has theirs every weekend during Advent. I would stay for a couple of days in any of these towns. All are located within an hour of Frankfurt.
Are you driving or taking the train? I would certainly do Dinkelsbuhl as a day trip from Rothenburg, perhaps you could then stay 3 nights in Rothenburg (3 nights is barely enough for me). The Rothenburg market is not really that big and it closes early (7 PM - at least some days - we barely got something to eat one night )