I think my question was unclear. I will try to clarify. (I don't have a plant in this situation, so please consider it a hypothetical question.) My thought is that as a phal. gets older, it will lose leaves from the bottom and will eventually be tall and leggy. In other words, it will have leaves at the top and a long naked stem below.
So, what do you do when a plant gets to this point? Do you plant it deeper, burying the naked stem? (I'm guessing not.) Will it sprout aerial roots higher up on the stem so you can cut the top off, pot it and have a fresh new plant?