Winter requirements depend on the species. However,most do well with a dry spell and cooler temperatures (above 10 Deg C.). A sunny window in a cool basement would be ideal. You might also Google "cactus and winter" to see what is suggested. Waz
personally i just put them under about 400W worth of full spectum lighting. they do reach a little bit, but nothing they wont outgrow after a month of spring sunshine and fertilizer. and only the fast growing cacti really reach anyway. cereuoids and their ilk