I can't specifically answer your question, except to say that, with great age, many evergreen azaleas will get quite big. They perhaps compliment boxwoods in that respect; boxwoods grow slowly when small but their clip might pick up after 15-20 years or so. OTOH Azaleas will relatively quickly grow to 3-4' and slow down, but I suspect most of the Indicas, given time, can hit 6 or even 8 feet. At the Tyler Arboretum in PA many azalea are up around 5-6'...and some of the rhododendrons much bigger of course. The picture from Charleston, SC in the link seems to show a variety of Indicas all at least 6' high.

Here is a link that might be useful: http://www.gardenclubbackbay.org/2014/02/15/friday-march-28-sunday-march-30-doin-the-charleston-azalea-style/

This post was edited by davidrt28 on Sun, Jan 18, 15 at 13:51