I'm a big believer in fundamentals and fundamental practice. I think it is less about what you play and more important to focus on how you go about it. Mindless wandering or doing the same thing with advancing to the next evolution is unproductive. The following bit is my take on the SAFARE principle shown to me by Ray Sasaki. I do not intend it to be a one size fits all but a starting point for someone who might need so focus in their practice.
Take one hour and dedicate it to your fundamentals. Break it up in the following fashion and see if you don't start to notice some better results. Having a plan is critical to the success of a practice session. Be sure to rest for a few minutes between sections to stay fresh. Rest before you need it. One great strategy is to sing each study before you play it. This makes sure you're really hearing it in your mind before starting and gives you a small break.
So let's begin...
Sound (10 minutes): Everything we do is a tone study. It doesn't matter if you can play high or fast if the tone is thin and unpleasant. Everything we play, every exercise, study, excerpt, solo, band piece, whole note, must have a beautiful tone. Long tones, flow studies, moving by half steps like early Schlossberg, take 10 minutes and meditate on your sound. Find the rich, resonant center.
Articulation (10 minutes): The articulation is the presentation of your sound. Single, Double, Triple. Long/short. Loud/Soft. Exercises like Clarke's "One minute G" or Technical Studies or any of the Gekker articulation patterns are great. Use a metronome to keep yourself honest and track your speed. This will help you see progress. Mix it up and get after it.
Flexibility (10 minutes): Here we're talking slurs where we change fingerings, lip slurs from partial to partial, lip slurs where we skip partials. Get out the Irons book, Bai Lin, or Colin Lip Flexibilities. If you want a new take and some humble pie, check out Scott Belck's books on Flexibility.
Agility (10 minutes): Scales, Arpeggios, Transposition, Changing articulation patterns. This is as much mental nimbleness as it is about fingers and coordination. Arban, Williams Scale studies, Clarke. This is a great place to mix in Jazz language. Check out Craig Fraedrich's book.
Range (10 minutes): Let's do expanding scales working our way up and DOWN. Don't neglect your lower register. You can't build a house without a strong foundation and you wouldn't try to put a roof on the framing before it was solid. Trumpet players are obsessed with upper register playing. Can you triple tongue a low G or F#?
I think Endurance is a by-product of practice and rest. I don't advocate making this part of a fundamentals session. We need to do some long line exercises, but I recommend Concone or Bordogni vocalises. Lyrical playing will get your chops together and can help fix some of the tension we can develop in the breath. While you play lyrical studies, you're developing musicianship. I've found this to be much more successful than isometric exercises out there focusing on musculature.
Be honest with yourself. Record yourself. If something doesn't sound great right now, that's fine. You're taking steps to improve your playing with one hour of focused, purposeful practice. If you don't have an hour, scale it to what you do have. Focus on where you need the attention, not what you already do well.
You've got this!