They do not always trunk up at the same pace...for example Gumpo is known to be one that doesn't trunk up well...sorry Kennedy...I have some from an old nursery...1 gallons..20+ years in a container...1-1.5 inch trunks....but very nice. I also just recently purchased some large gumpos for my landscape...3 gal cont, 2' tall and nearly 4' wide domes...no trunks much larger than a pencil in a group of 10. Where as, Chinzan are much more inclined to trunk up.... 3 gallon container, 10-12 years old 2+" trunks...when you can find single trunked ones...that is always the big challenge.
Jeremy...if the azalea you are referring to is your Kakuo? I suspect it came from a group imported by Bill V about 5 or so years ago. I remember that he reported they were grown in the ground for 24 years..might have been 25...there was an informational flyer with a picture of a long row of them in the ground...potentially your tree is 30 years old....of course, you probably know all this
john