You mention range and range alone. How about the musical parts--sound in the midle and lower register, dynamics, good 'ol basic technique? Do those change too? Please correct me if I'm wrong, but are you by any chance approaching the trumpet like a wanna-be bodybuilder instead of an athelete? You know, those guys that pop into the gym, bench press a while and don't show up for a week because they can't raise their arms above their shoulders for a week. If we approach the trumpet as a long-term project, adding just a half tone a month to our usable range will make us monster players in under three years. The same is true with other aspects of technique, so slow down, clean your trumpet (and maybe your mouth) out with soap, and try to approach trumpet playing with the disciplined respect it deserves.