I'm currently practicing to get ready for drum corps, but I'm having a bit of a problem. (I got braces off about 3 years ago, and since then I've practiced on and off, sometimes for a few months before stopping. I've only just recently become serious again about my playing.) I'll be playing along fine, then only about 5 lines down in whatever I'm playing (Cascades by Allen Vizzutti is one piece), my lips will start to feel tired and my notes all become fuzzy and airy, and it becomes harder to play the high-ish notes (G on top of staff). If I take my mouthpiece (Schilke 16C2) off my lips for even 30 seconds and then put it back, I can again play a few lines, and the problem will then happen all over again. Is this just a sign that my endurance needs working-on? Can you give me any excersises to practice that will help correct this problem? Thanks a lot!!