You are refering to Sub-c size battery right, is so then it's a bad idea....no good for your batteries plus it will rust.
According to the article, it say that if you wanted to store a fully charge battery for several months( not to prolong the life span) ie. It will hold the charge at 90% for months in a freezer and you don't want that well not for racing anyway.
There is a article on RCTech somewhere that tells you how to prolong the life a racing battery.
My procedure: To pro-long the life, I usually fully discharging it and then equalized after a run and let it cool down to room temperature before charging it up again. It 's a good practice to have more one batterys because you can have one discharging while you are using another one and via versa.
Hope this help...cheers