If you're not a brass player yourself, one rule that may not be obvious is to make sure that your brass parts, trumpets especially, incorporate rest at regular intervals.
Playing, especially loud or high, requires quite a lot of muscle strength in the lips, as the lips need to hold the tension for the note, and the higher the note, the taughter the tension.
Imagine lifting a heavy weight in the gym. If you get a short time after each time you lift the weight, you could probably repetitively lift that weight for quite a while before it got too heavy for you. Compare this to having to lift that weight continuously - you will run out of strength a lot more quickly. It's exactly like that.
If you have friends/contacts who are going to play your music, I would recommend asking them for feedback on whether the parts are ok, stamina-wise. Obviously how much stamina a player has will vary considerably, from occasional amateur to professional. Put it this way: the more strenuous you make the part, the more you restrict the pool of players who can play your music towards the professional end of the spectrum.