My COMC experience has been good and consistent. The shipments have all be scheduled for three months, but that is what was stated up front. Nov 2020 order got delivered in Feb 2021. Dec 2020 delivered in Mar 2021 and my latest Mar order is scheduled for July. COMC states they put a two week cushion in for issues and they shipped the last order two weeks ahead of schedule.
COMC just posted a new announcement of a new, larger facility and streamlining service options to try and get back to previous service levels. It took 2 to 3 weeks to get a delivery in normal times. But that will probably take a couple months to have a broad affect. COMC has been very good for mid-level cards and a few high end with most sellers taking reasonable offers and a few I have learned to leave alone. But shipping 100 cards for $6 is great and I am putting all my money towards cards not shipping and I just have adjusted to the fact that these are going to take 3 months to get here.
Each site seems to have found a nitch with Sportslots better for base cards as well as some other sites. eBay will probably always be first for lower SN, new cards just coming out and more expensive cards. Each site fits a need for what I am trying to collect at the moment. As for a delivery still hanging out from December, it's got to be coming soon.
Greg