Vizzuttii has an interesting perspective on long tones. They are OK, but don't over use them. They tend to fatigue the lip if held as a monotone. I personally use slurred long tones, one note sluring into another over an 8 bar phrase on one valve setting. Allen (Vizzuttii) tends to slur slowly on a scale pattern. Heard a lot of interesting perspectives during one of his 2 Master Classes he delivered at the Dayton Trumpet Hang... AND BOY DID HE DELIVER!