I have also found (especially since opened my Ardbeg) that evaporation is occuring at an alarming rate from my glass!

Last night i went back to my glass a few times and there was definatly less in it than when i put it down 3/4 min ago.

I put this down to having the central heating on.

The glass i am using is 'the Glencairn glass' which i highly recommend by the way, but maybe next time buy one with a lid LOL