My store has inventory turnover ratio of 8, so days of supply 365/8 = 45 days of supply. At CVS I got down to 35 days of supply (but was that DOS only for brand medications? I do not remember.)
I only order ARVs ahead of time for regulars or other brands for complainers who have a lot of otherwise profitable Rx. Unfortunately in California anti-psychs are carve-out meds for Medicaid, meaning a lot of Abilify, Zyprexa, and Seroquel brand.