Ogster, when you have grown your baby dracaenas, you can shorten the stems, and often will then get two or three heads in the place of the one that you removed. You will see little bumps on the stem. These are potential new growth, so cut to just above one.
And NEVER overwater. The die very quickly if too wet. Always let them dry out to at least a couple of inches below the soil surface before watering thoroughly, then remove any water from the saucer after a few minutes.I used to be an itnterior gardener, and we only watered some of our dracaenas every 6 wks or more. Always feel your soil before watering. Most plants will recover from quite severe underwatering, but will die if constantly wet, so go easy on the water.