I'm on my second pair of HD280s. The first pair had the band crack after about a year. At first I taped them together, but over the next 12 months the band really fell apart, so I sent them in and Sennheiser sent me a new pair. Supposedly the earlier models had brittle plastic in the band and they've since moved to a more flexible plastic because of all the problems. I've had the new pair they sent me for 2 years now without any problems, although I haven't used this pair heavily.
Its a great set of headphones though if you like closed ones, it sounds great and is pretty comfortable to wear for long times.