Results vary with details of circumstances experienced by shrubs before and after planting out in final location. Yours will not grow to a certain predicted size and then come to a standstill, either. In Japan they have camellia trees hundreds of years old, that could probably be used to shade a small building.

Here is a link that might be useful: The Myth of Uniform Plant Performance

I don't have Bonanza, but I do have Snow Flurry, which I really like. In my garden this plant has made a nice weeping mound. I planted it on December 8, 2002 and at that time it was 1'7" tall and 2'6" wide. The only input from me, of any kind during this time, was supplemental water during the horrendous summer of 2007. As of today this plant is 4'5" tall and 10'2" wide. No tag can pin down a size for every garden. Variety is the spice of life in gardening too!

Thanks