Overcorrection trays - why 3 weeks each? (Photo)

I just started overcorrection trays. I had done 26 of 33 trays, then refinements I was given 20 more. I am on tray 15. My results are pretty good tho I in my opinion, there are areas that still need correcting. When I picked up my last trays, my regular ortho was off (scheduling mistake) and the ortho on duty I never get straight answers from so I opted to just take my trays and leave, didn't even get looked at. He said 3 weeks per tray since "overcorrection". Is that typical?