I know that Wayne just answered your winter question a moment ago but I thought I should mention that the Red-bellied Snakes I've helped care for were successfully weened over to nightcrawler pieces or small worms. Like Wayne said, if they eat worms that have been in contact with slugs they think they are eating slugs. The red-bellied snakes I helped out with took a while to switch over -- for nearly two months we fed them slugs but always tried feeding them scented worm pieces first and eventually they started taking the worms. Luckily they started taking worms literally a week before winter hit.
Worms are of course just as hard to find in the wild in winter but much more available in stores