Wow that's a lot of growth. I've read Halley's Comet is a tasty variety. I have American Beauty. I've trimmed mine so many times, mainly because the branches were damaged in some way. Today the high wind broke off a large stem, that probably delayed the flowering another year or two
I read that its good to trim off the side branches and just have one leader stem, and once it reaches the top of the trellis, let it branch out again.