The oxynater diffusion stone

I have been using the oxynater for about 7 batches now and think it's one of those items you shouldn't be without. However, the stone doesn't seem to be releasing as much oxygen as it did in the beginning. I'm wondering if it's getting clogged or could it be the oxygen tank losing pressure the more it gets used. The oxygen tank has been used about 7 times but I have heard it should get about 20+ uses out of it. As for the stone I boil it every 3 uses for about 10 minutes, but I always let air run through it for a few seconds after aerating to help clean out the pores, and let it soak. If it is getting clogged anybody with ideas of how to get it unclogged, maybe boiling it in BBrite or oxyclean or something?

I think they do get clogged with time and I think soaking them in something (can't remember what) helps to clear the clogged pores. I'm thinking oxiclean but don't take my word for it.

What is up with the date and time?