I just had mine changed in my 2008 Bull yesterday at 134,700 miles. I have driven it 31,000 mostly highway miles in the past year.
My car was misfiring but not triggering any codes at all. It would do it intermittently at around 45-65 mph if I put a slight pressure on the gas without downshifting. I decided to replace the boots and plugs, had my trusty family mechanic do it, cost me $296 total.
I was thinking my car was having tranny issues, but right now it is running smoother than it has ever been and any appearance of slipping or hesitation has all but dissipated.
I would highly recommend doing so.