Just ordered a set of adjustable lowering links on ebay for $74 shipped. The only downside is the company is from Germany so they'll take a while to get here.
The original starting bid was $99 but I made an offer of 70 and it was accepted instantly so you might be able to get them cheaper. They look like decent quality.
Ebay lowering links

Ken- have you received/installed yet?? if so, can you show any pictures?? I'm interested in this mod, but worried it may cause premature failure of the airmatics. Not sure how this works exactly.

Yes, I just received them last week. They appear to be decent quality. All metal part and are zinc coated I believe.
Installation was fairly straightforward. The front took about 20 mins. I just lifted the front of the car, it's not necessary to remove the front tire.
The back took longer because it's a fairly tight spot. Also failed to read the instructions which added time because I assumed longer = lower, like the front, but it's the opposite for the rear, shorter = lower. So it took a lot more adjustment. I got pretty good at it now ​​​​​​. I found using a skinny telescoping pen magnet to be extremely useful aligning the upper socket to the mount.

As far as excessive or premature wear, I haven't read any complaints on the forums or anyone saying they've had an issue after install. Depending how low you go, an alignment might be a good idea.

I lowered mine approximately 2", I forgot to measure factory height before I started. Measuring in the center of the wheel, It's currently 26 inches from the ground to the fender front and back.
This is with the car running, in sport 1 mode and someone sitting in the driver's seat. So it shouldn't go any lower while driving.
When I turn the car off, open the door or trunk, it'll level itself and drops about a 1/2 inch.

I'll get some photos tonight or tomorrow when the snow melts.

Oh, it's worth mentioning. The MB dealer can lower the vehicle through the ecu. I don't know off hand how low it can adjust it this way but there is a limit that has been mentioned. Cost varies by dealer ($150ish?) some dealers may not be willing to change it due to liability.

looks great!! sorry, been a busy work week. Doesn't sport II mode go even lower than sport I ??

also feel free to do a write up if you ever are under there adjusting them again. For the simpletons like me.