You know, I keep thinking about a comforter... but I was so alarmed by the reading material that was so DIRE about leaving anything in the crib with the baby to prevent SIDS - including crib bumpers, which I would love to have in there, because she wiggles herself up to the edge and then thumps her head on the bars while she's squirming... goofy baby. What age do you start with a comforter?