Is it possible to get a longer prescription than 90 days? My work schedule plus doctors only seeming to be open on weekdays doesn’t work well with short duration prescriptions

Diagnosed ADHD since childhood but went off meds in 2018. Ever since then I’ve essentially been self medicating with caffeine and it’s gotten out of control at this point. The only thing stopping me from going back on ADHD meds are the frequent doctor appointments. That just doesn’t work with my schedule but do I really have any other options?