Well alot of factor can change this; The light cycle you use?; The nutes; Will you use superthrive or not?... What kind of light? Will you adjust your light as plants grow?
Ive grown 7 footers before (see my Avatar Pic) .... they like be vegged to about 24" before flowering though.
Keep em short, dont over prune - they flower good buds at every tip !
I'm pretty sure most of the white family (including my white rhinos) tend to be booked in the 'short' category when talking about overall height. It does however depend on a lot of various factors, but if you want an average, I would say 1.5 - 3ft.