My questions are these: Are there tandem only rides? As a tandem team do you ride by yourself during the week and on weekends? While this may me jumping the gun anyone done the ride across Iowa on their tandem. We were thinking about this ride on singles and I"m not sure how much harder it would be on a Tandem.
Tandems only rides are rare but they do happen where there are active tandem bike clubs. I do neighborhood riding with the wife and kids and we are pretty much always the only tandem. If you are already in shape to do a cross state ride on a single bike then you should be okay for completing the same trip on a tandem bike. In fact, if you're touring, it would likely be might be more fun.