I see from Longbike's previous post that the team currently rides a Burly. I think that it is more the tubing on that frame rather than the age that is the issue. A high quality frame of the same vintage from Santana or Comotion would for me be a large increase in performance. Even when new Burlys were budget tandems with rather thick walled tubing compared to bikes like an Arriva or Speedster made with 8/5/8 tubing. The Burly tubing is much heavier and less lively. Regardless of the era, there is a big difference between a dependable heavy steel bike and a performance steel bike made with thin walled tubing.