The various notes were interesting but the base facts vs personal preference are you major concerne. To quote an old saying "there's more than one way to skin a cat".
The reality is your drive train is being powered from the road drag instead of the engine. The system was not designed to work that way if it drives all the way to the engine. It is a big advantage in the world of manual transmissions because it is this reversal of the power train that allows us to push start a vehicle. That is impossible to do in an automatic. Up check for us.
The entire reason I just purchased my 87 Wrangler project vehicle was for towing behind my class A motor home due to its true neutral drive train capability. The transfer case, when placed in neutral as described in the owners manual, is a quick easy set up and it was designed for that. A thankful historic throwback from the war jeeps that were also towed frequently. They didn't have a lot of time to find a wrench and unbolt the u-joint let alone put it back together. The war usually doesn't come with a time out period. Being a firm believer in Murphy's law, I personaly prefer to leave the transmission in neutral as well. A good suggestion by one of the other commentaries.
You must remember that in towing flat, the differential will always turn and the miles will pile on but the odometer gets it's reading from the transmission. The "output" shaft of your transfer case will still spin from the drive shaft and of course the milage wear on that portion too will add up.
If you wish to spend the time, obviously disconnecting the drive shaft reduces the wear on all parts including the u-joints but not the diff, axles or tires. One response mentioned that the drive shaft was wearing out the wire it was hung from. You want to disconnect at the diff side, not the transfer case side. Make sure only the shaft flange is on the spinning side (at the diff) and no bearings are attached. This of course is time consuming. Advantages depend on the tow distance but I for one do not intend to mess with it.
In the RV world, a toad (clever RV groupy synonym for "towed vehicle") is so common and the expense of a trailer sometimes not prefered that there are companies specializing in towing equipment for automatic transmissions and I believe manuals as well. They include special drive shaft disconnects that can be actuated from inside the vehicle and remain permanently installed. You can imagine that an older couple does not prefer to crawl under the toad and mess with it. Look in the RV magazines and I know you'll find at least one. Try REMCO. They advertise as the towing experts and sell these devices. Their web site is www.remcotowing.com
or you can call at 800-228-2481. They are operating out of Omaha, NE. I personaly have not used this product so I can't speak for it from experience.
Good luck with your choise. I hope I sheded a little more light on the subject for you.
Tread lightly and stop to smell the roses - Traveler