Ok, so I've been on the comeback trail for about a year now. I play with my church brass ensemble. Not surprisingly, I continue to struggle with endurance. We just got new music to practice for the upcoming easter season. The first piece (The Lamb), is not at all difficult, but it's 116 bars (incl. repeats) with 22 bars of rest. Not really that long but it's a struggle for me to get through. It's not so much that my lips give out, but the sides of my face start to hurt. I'm sure it means too much tension, but if I relax my face any more, I can't make a sound. It's frustrating because my sound and technique are as good or better than they were 25 years ago. I've been playing from my Lutheran hymnal (Rowuk's suggestion). Maybe I just need to be patient.