I read somewhere about a method for speeding up steeping by submerging the bottle inside a baggie into some hot water for a little while. That, and keeping it in a warm place while it steeps (warmer than room temp). Personally, I keep mine in a tin leaning against the furnace for a while. It stays warm there for a few days, while I shake at least once a day. After that, I move it off the furnace, but still near, so it stays warm for the remainder of a week or so. I shake it violently every day. If it's still losing flavor, I may give it a few more days of warmth or add more flavor, or both - whatever I feel like.
All that being said, I don't know what I'll do when this awful winter is over and the furnace isn't on all the time.