I think you're still a caffeine hound and that's why you are keeping
that decaf tea bag going even through a second cup. ;-)

Still, I kind of doubt you are getting a buzz from the caffeine. Do you
get a buzz from a 12 oz. cola (30-35 mg caffeine)?

Since most of the caffeine is gone in 30 seconds (as already mentioned
here), I don't think you're getting much more by steeping the bag
continuosly. Over steeping causes bitterness not elevated caffeine.

Now, maybe if you put 6 or 7 of those bags into 6 oz of water, I might
believe you're getting a caffeine buzz. ;-)

See the DIY decaf method in the tea FAQ -
http://pages.ripco.net/~c4ha2na9/tea/faq.html#5.6.6.