Originally Posted by SnidelyWhiplash
my concern is after 90% of the fermentation it won't be going fast enough to keep it warm, and the yeast will quit working early because of cold + high alcohol.
Lager yeast still works that low, it just needs extra time, so leave it in longer after fermentation seems to be finished for it to fully attenuate.
Like stonehands said. Then it won't need to be removed for a diacetyl rest.