What would cause a yeast to not fully attenuate? I have an IPA with an OG of 1.061 and after 2 weeks I am (only) down to 1.019, giving my yeast an attenuation of only 69%. It has been fermenting at 64-67F. I am using WL051 from a 2 liter starter. The White Labs site states this yeast should attenuate to 70-75%. I want to squeeze more ABV out of this beer. Is 68% good enough, or am I obsessing? Could I raise the temp. to say 70 or 72?