Personally, I would not do it. In my car, 1992 300TE 4matic wagon, if you disconect the 4matic, you also disconnet the hydraulic self leveling suspension, which will affect handling, etc. Plus, because the car is so damn heavy, I doubt you'll see much of an improvement in gas mileage. Plus, any "wear" you save may result in a loss of lubrication somewhere, (guessing), which might cost more to fix. (For example, in older, pre-1980 4x4's, it was important to run them in four wheel drive every month or so to lubricate the front differential; failure to do so would inevitably cause problems later). Here, you should do a "4matic" search in this forum and you will find lots of discussions about this idea and others that you will find informative. Good luck, and if you decide to try it, please report your success/failure and any improvement in acceleration or gas mileage. All us 4matic devotees will be waitng to hear what you have to say.
1962 Mercedes 220SEb "Fintail" Sedan
1963 Vespa Scooter VNB4T
1992 Mercedes 300TE 4Matic Wagon
1995 Subaru Legacy Wagon