My Witchy Cauldron crafting options disappeared at 6 pm PT - NOT the 8 pm PT deadline that was listed for each of the crafting items. And after 6 pm, I stopped getting any event drops while doing the weekday warrior tasks.
I had an item in the cauldron crafting that was going to finish up shortly after 6 pm, but I was nervous that the 8 pm deadline didn't sound right. So I gemmed it shortly before 6 pm, which is the typical time for events to end. Glad I did.