I keep repeating the theme that in order to not neglect certain playing techniques, we must include these techniques in a specific slot in our regular daily practice schedule. I have previously mentioned techniques such as lip slurs and single tonguing. I feel that it is also important to ensure that we at least include a minimum amount of pianissimo and fortissimo playing every day.
Pianissimo playing requires embouchure control, steady breath control, and suppleness and responsiveness of the embouchure. Fortissimo playing requires, in addition to strong air support, embouchure strength and the ability to control the aperture when subjected to a large volume of air. In short, the extremes of dynamic range require totally different types of physical control. Obviously, the only way to develop and maintain control at these extremes is to practice at these levels, for at least a few minutes, on a regular basis.
I would speculate that most trumpeters who are reasonably accomplished, spend the largest proportion of their daily practice time playing mezzo forte or louder. The reason for this is that their sense of good solid air support will most naturally result in a full, resonant, and somewhat loud tone. (On the other hand, it might be a good idea for less accomplished players to consciously spend a greater amount of time playing at loud dynamic levels to develop a better sense of good air support). It is my belief that these accomplished players may need to purposely include some supplementary pianissimo selections every day. Likewise, even if a player does much of his performing at a loud level, he will not be able to control those fortissimo passages when called upon, unless he has included at least a little fortissimo playing in his daily routine.
Personally, I can discipline myself to include tonguing and lip flexibility exercises in my daily routine, but to include exercises that are designed solely for the purpose of playing at loud and soft dynamics is, for me, extremely boring. I really prefer to cover my dynamic extremes by playing selections from actual musical examples, orchestral excerpts for example.
I would like to suggest that you pick a few of your favorite excerpts which represent extremes of dynamic levels and play them at a specific point in your daily routine.