Now, this is all just realm of speculation, but I have been researching the action of charcoal in filters and elsewhere. Apparently it is used for the Purification of helium gas. I would venture to say that helium is NOT adsorbed by the active charcoal. It purifies the helium of impurities by adsorbing them, while allowing the helium to pass. Also, helium is a noble gas, meaning it does not react well with anything and usually adopts an inert state.
So, running by this logic, I have some newer production DPG-3 filters that i have loaded with helium from a balloon tank. Also I put them in vacuum sealed packs, like the kind for freezing food in. I have no idea if it will keep them fresh for longer, but if it works, then they may stay fresh for a long time.