See pix at
http://webebananas.com/culture.html Section 5. Each variety is different - some have large plants with few roots, and some have small pups with a lot of roots. I have had 6 inch pups that didn't fit in a 15 gallon pot, and 5ft pups that could fit into a 1 gallon bucket. Pups over-wintered usually have more roots than new pups emerging in the spring. You have to get to know your variety.