One thing you should check from time to time is the quality of their bedding. The bedding should be moist at all times. After about six weeks, the bedding will start to change noticably. After a while, the worms will have eaten most of it and turned it into worm shit. Although some people can live in these circumstances, worms can't cope with it. When your heap approaches this point you have two choices. You can either write this batch of worms off and start anew, or you can try to save the worms by fixing their home up again. According to bianca's friends, it takes about 3 or 4 months for the worms to eat through their original bedding. So, if you choose to let your worms die, but want a year-round compost system, you'll have to buy 3 or 4 batches of worms a year.
bianca doesn't think this is too economical, so she prefers the higher- maintenance method of trying to keep the worms alive. The system is simple. After about half of the bedding has been eaten, push the whole mass over to one side, put new bedding in on the other side, and cover the new bedding with black plastic. The worms will work on the new bedding for awhile, and when that starts to look bad, take out the really old stuff, move the newer stuff over, add brand- new bedding and cover it. Do this every two or three months and you should have a self perpetuating system.