A question so obvious that I feel silly asking it, but you didn't pasteurize the cider before bottling, did you?
How sweet is enough? You could re-inoculate with new yeast in the bottles if you are sure that you're not lighting a fuse for bottle bombs. I have done that with a Belgian Dark Strong that had all of the yeast die in bulk aging.
Primary: Too many sours to mention.
Aging: Mead, Flanders Red, Belgian Dark.
Serving: Too many to mention. Dry Cider, East Coast IPA and Old Ale are my current standards.
BJCP ID: F0785, Certified Judge