My father bought a pair of those in 1969 and ultimately I ended up using them quite a bit in the 80's when I was a kid. I think that pair lasted until about 1992 when they had to be retired, since after a cord replacement or two, the outer housing cracked and they were done. Of course the foam cushioned ear pieces had hardened as well.
In the mid to late 90's I bought another pair in pretty decent condition (i.e. the cushioned ear pieces were still soft) and used them until 2001 when they were stolen from the college radio station when I had accidentally left them there after my show (someone broke all of the stations cans, so we had to provide our own). A few years later I bought a NOS set off of eBay and still have those.
For the era those headphone were made, they're phenomenal, although they have a bit of that "barrel effect" that was associated even with the best headphones of the era. I have newer and better cans, although I do like the sense of nostalgia I get when I listen to these.
