DIY C02 recipie doesn't last

This is for all the DIY C02 users out there.

I'm running one bottle on a 75g and one on a 50g. The recipie I got from a FAQ 
file off of the AquaLink web site calls for 3 cups sugar and two tablespoons 
yeast (roughly 1 packet) to the two litre bottle. The file states that this is 
supposed to last about two weeks. I'm barely getting one week on mine.

Can anyone give me their recipies, tips on stretching out the time between 
refills, etc.. My wife says to add more sugar to the bottle. I also thought that 
placing the bottle on a heating pad might increase c02 output, but then again, 
that might just make it burn up faster.

Douglas Duncan
email: duncand at sprynet_com
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