I have owned and serviced 6 Triumphs, 5 x 955s and my Tiger 800xc. they have all needed some adjustment at 12,000 miles and I tend to aim for the upper limit when replacing the shims and even change the ones that are within spec if I can get them towards maximum without going outside of limit. Once this is done they usually stay within spec for many miles. My Sprint RS has now passed 60,000 without further adjustment.
Not checking at the required service mileage is risky, despite what people may tell you. Valves that are too tight will cause poor starting, reduced performance and eventually burnt or bent valves. Too loose and they will be noisy and again loose performance.