Pragmatically On a tour, Here in this town on the very popular Pacific Coast Bike route we have zero Campagnolo spare parts .. it aint Portland.
so overspending on a bike will bite you in the spandex if there are problems on the tour. (Idk about fully supported tours Never done any)
for those who show up here needing stuff not in stock we work with the next big (?) town
Down the Coast and call that Bike shop, they special oder the stuff and the rider limps a couple days south on their bikes ,
and hopefully the order has been Expedited to be there..