I was just having the same problem with my new Home Depot cooler I put together and used on my AG brew saturday. I went from 151 to 144 during the hour even after pre-heating the cooler. Still got my expected OG of 1.070 per the recipe, so I'm not complaining!
That government is best which governs the least, because its people discipline themselves. Thomas Jefferson
On Deck: Bavarian Hefeweizen
Primary #1: Edwort's Apfelwein
Primary #2: Green Flash West Coast IPA
on tap #1: Addicted Coffee Stout
on tap #2: none :(