btw, this is my rear after 1 year 4 months of no cleaning. I finally had to raise them up and gave them a good cleaning and the threads look as good as the day i got them
What i did was get some brake cleaner and sprayed it in the threads to get all the gunk out, then got some spray lubrication to put in there. There was some brownish gunk in there that looked like rust, but i just moved the thread over it and kept spraying the brake cleaner to clean it out. I moved the plates from almost all the way from the bottom to the top. It did get difficult near the top, but just make sure you keep on spraying some brake cleaner because the gunk builds up as you keep turning the plates.
Basically, take care of whatever you get. If you want to keep height adjustability, move the threads at least every year all around and keep them clean and lubricated.