Personally I always thought that triple towing is risky at best, especially with the hitch & tow bar of the typical travel trailer and boat trailer. It works well enough going straight down the road, and OK in cornering as long as you pay attention to what you are doing and have plenty of room, but what happens if you ever have to swerve or slam on the brakes? Trailers can get awkward in a hurry when there is only one of them; having two back there when the crap hits the fan is not something I want to see or be anywhere near.
But then, I'm a bit conservative, having had a trailer jackknife and tip over on me once after a seemingly minor emergency. My wife was driving at the time and her trailer handling skills were not the best, but it sure made a trailer safety believer out of me!