Interesting subject.
I fished the Letort first back in the early 80's I would estimate, and fish it only couple times a year, more often in the cold season lately.
As Dave Weaver noted, there is variation in weed growth and flow level from year to year and season to season, but not much as changed in the the past 30+ years from my perception.
What do the long-timers and regulars on the stream see?