Hi Blaine,
My Lector was used for appx 100 hours when I got it; I did not notice any change or break in periode after that.
Tube rolling may be the way to solve the edgy upper midrange.
I was using the Meridian 508.24 as well and this player seems smoother and less edgy in the upper mids - until I started to recognize that the Meridian in fact rolles of, giving this more soft and laid back feeling. With the Lector you are seated in the 2. row, with the Meridian (or other more laid back players) you are in the 15. row......the choice is a matter of taste.
I did try the Mullard as well, giving a more soft and Meridian like sound, but missing some of the very best with the Lector; the transparency and crisping and "airy" musicality (difficult to explain, my native language is norwegian *s*) My best choice so far has been the RFT tubes.
Another experience I have is that the lector works best with a tube pre, towards the warm side.
Good luck!
Ole