You shouldn't be tired by the end of rehearsal -- not if you're practicing properly and focusing on breathing properly to play well. I played on Bachs for years, principally using the Bach Megatone 1C for the past 20 years until I attended ITG convention in Harrisburg and had a chance to try a lot of different mouthpieces. I settled on a Laskey 84B and have been working on that for the past 5 months and am feeling better and playing better than ever with it. I was using a regular Bach 1C (had been since college, 5 years earlier) when I tried the Schilke 14A4a on the advice of a friend who loved it. I used it for about a month or so but could never get used to the different shape of the rim and went back to the Bach. I have since found that my mouth isn't comfortable playing on any mouthpiece without a Bach-type rim.