They grow back double, though smaller. When the plants get big. I generally cut just above a node. The stem above the node is going to dry up anyway, you don't want the hollow stem to fill with water and rot. Any place you cut, new branches will sprout.
Harvesting is a good time to start new slips.
Say you cut off a four foot section of stem. Break off the top eight to twelve inches or so, pinch off all but the small leaves near the top, and drop it into a glass of water. If there are four or five such slips in one glass, they seem to stimulate each others root growth. When the rootlets bud out, you can pot them. I never use rooting compound anymore, though there is no reason not to.