Dr Towe, I believe that he is referring to this article from Chemical & Engineering News: https://cen.acs.org/environment/sustainability/find-hacks-greening-lab-start/96/i35
Dr Kolwicz -
I think it really depends on what you're storing and how long you plan to keep your samples. If you have several freezers, you might consider setting all but one of your freezers to -70, keeping the most sensitive and long-term samples in the -80 cold freezer and your shorter-term projects in the -70 ones.
Also, I didn't see this mentioned in the article, but setting an "expiration" date for all samples is really important to free up freezer space, improve air circulation inside the freezer and reduce the need for additional freezer units. I have first-hand knowledge of samples being left in freezers indefinitely "just in case", even after researchers have left an institution! Freezers need regular maintenance -- thawing, cleaning out, preventing ice build-up, etc. This is often overlooked, especially with walk-in freezer units and "inherited" lab spaces.