So when I'm practicing I now use the system where I play like 20 minutes , or a set period of time and then allow for rest and then I repeat. When my lips start to get really tired my articulations, usually starting at about an F on the staff, start to become really really bad and the more fatigue I continue to accumulate the more delay there is between the time when I tongue and the time where tone starts to produce and my lips buzz. Eventually it escalates to the point of I can't tongue high notes mainly above an A above the staff at all and just air comes out. So I have 4 questions concerning this issue. - If I want to get better is it ok to practice in this lip condition? - Since my articulations start to suffer and my range dies out what can I still practice at this state of bad lip strength? As in, should I try to work on things more demanding like double tounging or take it easy and practice lyrical stuff and long tones? I would also like to add that lower notes still have my same tone quality even when I'm tired. I don't sound like a train wreck, but I just can't play high well. - Is the goal of a long practice session to make your lips sore? Should my lips feel sore at the end of a PRODUCTIVE practice session? - Is there a limit and a point where I can damage my lips?