I had a Kolsch that didn't drop krausen after 3 weeks. I've heard that cold crashing it will help it to clear and drop, but I didn't try it. I just racked underneath the foam into secondary, since my 5 gallon carboy fits in the fridge for cold conditioning time.
Primary #1: Empty #2: Black IPA
Secondary #1: Blackberry Rhubarb wine #2: RIS #3: Cab MerMarqeNac Wine
Kegged: Pumpkin Ale, Pre-Prohibition Lager
Bottles: Carmel Apple Cider, Big 50 Barleywine, Framboise Lambic, Barolo Wine, Berry Rhubarb Wine, Black Currant wine
On Deck: BGSA