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Craig Calfee started making carbon bikes in 1987 and were ridden in the Tour de France in 1991 so there is certainly a history for carbon as a frame material for well over 20 years. I believe he made some tandems in the late 90s. It all depends on your desires, we rode every frame type on singles for many years and when we decided on a tandem we liked the way our carbon singles rode the best and we had a carbon tandem built and have never looked back in regret (about 15k miles on it). Our kids have aluminum tandems and can drop us at will and they enjoy the ride however they are younger and more resilient. We have done numerous centuries and beyond and the bike has been on four continents and the durability and dependability has been fine. With the same components and wheels etc the rides of the various material are going to be similar enough that the best thing to do is get a bike and ride it!!!