I have one of these and have learned that these are very prolific growers. After you allow it to attain the height you want, you will have to address the size of rootball at some point. Even though you trim the top, the roots will keep on growing. The roots will have to be pruned after every few years to fit the maximum size pot you wish to use.

I topped mine this past fall at 4' and just pinch back the new growth at the cut. My current pot is a 14" and the tree will eventually be put into a 20" pot which is the maximum size for me. My tree is grafted onto a semi dwarf rootstock while yours is on it's own roots. You will have to root prune more often than I. Root pruning will probably have to be done about every 2 years.

I agree with Denise, you'll just have to upkeep the tree a bit more if it is on vigorous rootstock or is itself a vigorous grower. I'd look into root pruning techniques and get comfortable with the process, this will let you keep almost any tree small(er) in a container. It's one of the chief principles in keeping bonsai trees small