Range practice should be incorporated into your daily practice, just like breath control, long tones, flexibilities, reading, etc….. To keep what you already have active and sounding good and to add a little to keep your muscles in the memory discovery mode. This, with a lot of patience is how you gain the healthy range you want. As everyone above has said, it cannot be your priority, there are too many other very important aspects of playing you need to concentrate on right now, and range comes with learning everything else correctly. I was one of those fortunate guys in HS that had natural chops and a high range, (and a Dad and Brother who played professionally). So I sat lead for years, but I had to practice everything that we are all talking about to you, even the natural guys have to practice the right stuff.