By participating in the Freezer Challenge, you are reducing energy consumption, operational costs, and environmental impact of the lab. Efficient management of samples and freezer units reduces wear and tear on the unit and increases the freezer’s longevity, resulting in less repairs and fewer replacements which increases sample stability, security, and integrity.

In terms of sample storage temperatures, storing samples at -70°C has been shown successful across multiple sample types and temperatures, whether this be the storage of microorganisms or proteins.

By storing at -70°C you improve temperature stability and sample security, decrease freezer duty cycles and compressor stress resulting in safer samples, lower power consumption, longer freezer life, and lower operational costs. 
See this summary poster which shows Stability of Genomic DNA at Various Storage Conditions may be stored at -20°C.

For more information regarding efficient freezer storage checkout the resources listed here.

The International Freezer Challenge website has also provided a detailed spreadsheet of samples that have been effectively stored at -70°C, -20C and 4°C throughout the past 20 years or so. If you have experience storing samples safely at warmer temperatures join the international research community tracking these safe and sustainable cold-storage practices by contributing to the “Biological Samples Stored Long Term at -70 C or Warmer”