It may Don if it is not 100 % sealed and can pick up moisture or where gas can diffuse into it. But I have never seen it or heard of it. Maybe you just got a bad container of it. Is the BD getting hit with crap loads of ozone ?
I have some new GAC that is almost 20 years old. I'm looking at it now. I have opened these containers many times and they are still prefect. Mine are all in plastic screw top containers like BD. And I have all forms of GAC, coarse, fine, Lignite, CC, ROW (ROX), Bitum, acid washed, not acid washed and from Norit, Calgon and Barnebey & Sutcliffe ( an importer and have not been around for almost 15 years, bought out by Calgon) and AtoChem/Cecarbon ( a USA manufacture, also not around for 15 years, bought out by Norit). I pulled out a few grains from a few and just ran a test on hardness with a small Mortar & Pestle and they are fine, nice and crisp.