I trim ours every year, although I do not butcher them. There is a correct way to trim them to keep them shaped & their height 'in-check'. Here we trim them the last week of January (before they start budding out) by cutting 2 inch above the previous years cut & then thinning them out before shaping. They respond very well to pruning, with vigorous, strong growth & near continuous flowering. This is a picture of our 'Red Rockets' from 2008.