With my winter bike I'd done over 3700mls before replacing but that was probably a bit late in my case. On my summer bike as I was doing an event, the Etape Caledonia I replaced my grand prix's a little premature at 2750mls. IME I'd get more out of them than 2000 miles but for that peace of mind its worth changing them before the Maratona Dolomiti, you've made the right decision.