Shouldn't get shorter with use - unless you start dragging them across the build platform constantly - even then I am sure you would notice that


I thought the head height could be adjusted - was reading on here last night a lot of posts and came across it.
There is a set screw in the aluminium plate above each of the heads. you can loosen it and then move the head up or down. It is on the front on mine (I noticed it last night when I had made the mistake of trying to print Ninjaflex and it wound around the motor - Doh! - will give it another go tonight now I have found the fix for it ). There are two black allen heads right in line with the print heads.
Will see if I can find the thread a mo.

Ah here it is:
http://3dprintboard.com/showthread.p...ighlight=screw