As I wrote on another post:
My instrument is realy responsive and easy to play in all the registers, from the bottom to the highest altissimo. However, after 2 years with it, I know that the problem of me sounding like im losing my embouchure after several minutes of playing without stopping, is in my horn. I know that because I work realy hard on long notes and overtones, and a friend of mine which is not doing this at all but play a selmer, doesn't have this problem.
We switched instruments for a week and his selmer made me feel so free, so in tune, like it prevents you from losing grip. I realy liked it (it was a silver series II)
I played a clarinet for somthing like 8 years and switched to tenor in the last 3 years, so after that and after playing hours a day on the tenor I realy feel like the problem is not me.
(also, I switched some mouthpieces/reeds/ligs, and found this seutp which lets me play with the least feeling of embouchure loss).