" BTW - for what it's worth, I have one of those "needle valves" from Home
Depot. I'm already starting to suspect the problem might be somewhere
there. It's not even really a needle valve, so the control is less than
desireable. I'm not quite sure how they can even be marketed as a
needle valve. Tell me folks, is it in the valve?

If you are using any check valve, that could be the problem too.

I am using the same "cheapo" home depot needle valve for the past one year
and my 5 lb. tank is coming around 6 to 7 months. My output pressure is 15 -
20 psi. Currently I have 80 bubbles per minute. I would suggest you to
tighten the top "nut" (the one below the 'T') if you really suspect the HD
needle valve.

Post your findings.

--
Thank You

Dominic
http://www.dlink.org/aqua