Lips & your embouchure are muscles... just like biceps and thighs. Think about trumpet training the same way you would about weight training or training for any other athletic endeavor. You have to give muscles time to rest and recover. . You gradually build up intensity, reps, and time to build up strength & endurance. I played one summer in college in a band in a major amusement park. We did 9 shows a day, each show was 30 minutes... then 30 minutes off. We got 45 minutes for lunch. I was a pretty strong lead player at the beginning...The book was pretty strong and we were hot dogging excessively. But after 3 days I could hardly play a note. By the end of the 1st week I almost got fired, but the guy running the gig knew me so I got to stay. Over the weekend I soaked my chops in slurpees & sucked ice cubes then played some pedal long tones. And time off. The second week was tough too, but better. By the end of the summer I was super strong and fresh even on the last set of the last day. You can't goof off all summer, then show up in the fall and start playing 4-5 hours a the day out of the blue. You have to get in shape, and then STAY in shape. If you were playing a flute or a banjo I'd say no problem, but brass instruments require a more athletic training routine. Use it... or lose it!