Thanks again, you two.
The reason I specifically asked about 737NG is because I fly (down the back) in them rather more than I care to admit and I believe there has been a tendency with my preferred carrier over the last year or two to report in their little captains announcements that we are at 38000 and a few times even higher I think more often than in the past, despite me looking round the cabin and thinkng well hey, we're pretty full!
And whilst sitting high up there nice and pretty and stable in very smooth air, perhaps in pursuit of a jetstream or trying to cruise above one, I have many times felt us go through a patch of slight clear air turbulence or buffet and I've often thought I wonder how near the top corner we actually are, because I know we are well above the weather so that just leaves CAT and other things that I am just not sure about.
It seems to me my chosen carrier has also been achieving regularly shorter airborne times on my preferred routes. Where it used to be 1:20, 1:25 on a particular route, it is rarely so long now - just a feeling - I know that various and delayed approaches at the busy end of the route can affect the airborne times tremendously.
Either the aircrews or the ATCOs or both seem to be getting very good at what they do.
Maybe I hadn't noticed, and load factors and other changed practices have brought the weight down, so 38000 is an obvious place to be.
Maybe I am just plain wrong with my "feelings".
But sometimes right up there, I've felt a little uncomfortable. Maybe its just the cosmic rays that have finally got to me
So that's more or less why I asked in case you were wondering.