The wait times seem to be based on Axiom's planned manufacturing schedule and the expected cosmetic fallout rate. Sometimes the wait can be very short if they are planning to build the models you are interested in soon.

M60ti, VP180, QS8, M2ti, EP500, PC-Plus 20-39
M5HP, M40ti, Sierra-1
LFR1100 active, ADA1500-4 and -8