muzikborne2...here is my take on this. Lip buzzing and even mouthpiece buzzing are a quite different to how your lips actually work when producing a tone when the trumpet mouthpiece is in the horn. You shouldn't expect the lips to be functioning in the same way (You may see different opinions about this, I have seen famous player/teachers disagree about this point). I recommend keeping lip buzzing to a minimum, no more than two minutes per day. Focus your time on playing with the mouthpiece in the trumpet and producing a good tone. Practicing chromatic scales, or any sort of scale, slurred and very quietly with a crescendo as you ascend and descrescendo as you descend could be helpful too.