I don't know your site conditions or climate, but have you considered whether or not you even need freezers? Here is an example of a root cellar at Sepp Holzer's Kramaterhof. @ 15m25s
There should be drawn plans and threads about this all over Permies.com.
If you want to make sure your stuff stays frozen but doesn't use much energy in the meantime I think placing freezers in a cold location makes sense and using older ones extends the life of a product created with energy-intensive manufacturing. The plastic has probably off-gassed it's VOCs so placing it in an area with less air circulation isn't a problem, in my opinion based almost entirely on theory.