Joprras : The perceived loss of highs could be the result of "dirt" clinging to the record surface, "dirty" steam , improper steam cleaning methods or most likely records that need additional cleaning. Rarely, I have cleaned a Lp where gunk clinged to the grove requiring further steaming. This does not happened often but can happen.
As for the posting regarding a 6 hour difference between plays , I recall several articles in the late '70-80's in "Stereophile" that claimed recently cleaned or played LPs require a "rest" period of 2 hours or so for the vinyl grove to re-shape to pre-playing/cleaning condition. So, it not as if the phenom has not been remarked in print.
