72" is the longest I've been able to come across, and only then it was the one you told me about. Kepur straps are the longest I've used and their website http://www.coreoneproduct.com/pages/kepurweb/kepurhome.html
says the longest ones are 62".
Kepur straps are awesome. Really heavy duty stuff. My Warwick bass is probably 10 pounds and my 3" wide Kepur 5.zero strap rocks my socks (I have one with the sparrow). The 1.zero straps are 2" wide and have more variety of designs on them. The serpent one's pretty badass. I actually had to modify my strap so it'd be shorter. It's perfect now. I'd recommend Kepur straps to anyone. I dance around with my bass, jump into the crowd, and writhe around on the floor whenever I perform, plus my bass is heavy so I need a strap that won't quit. (Straplocks help too; I like the Dunlop ones.)
I think Ernie Ball PolyPro superlong guitar straps are 68" at the longest, but they're cloth based.
Most leather straps I'm aware of like Levy's or Moody's are 54"-60" at longest. Moody straps are insanely expensive. Levy's are a better value for the money, though they don't come cheap either.
EDIT: for reference, shortest bass straps I've seen were 33"-35" or so. The shortest bass Comfort Strapp goes from 33"-37." By contrast, the guitar ones start out longer. http://comfortstrapp.com/products.htm
It's funny how the strap's the most overlooked aspect of a guitar or bass player's arsenal. A good strap wards off back pain, that's for sure. Never skimp on straps or strings:P