What are your samples worth to you?
Can you put a value on the contents of your ultra-low freezers? Odds are they're irreplaceable to you, but in monetary value the contents of a single freezer can easily be in the tens or hundreds of thousands of dollars.
Traditional ultra-low freezers rely on a single compressor system. If this system fails, the freezer and your samples are out of luck. LN2 or CO2 backups only sustain temperatures for approximately 7 hours, and require routine re-filling. Twin Guard® Series freezers house a second, independent compressor system. The two compressors work together in normal mode, but if one fails the other can maintain ultra-low temperatures for an extended period of time.
RYskU5 on Make A Gif, Animated Gifs

So, what's a compressor system?

Simply put, a compressor is what runs your freezer. It's the heart of the whole system, keeping your freezer at ultra-low temperatures.
Traditional
Compressors are traditionally made up of two parts: a
high stage and low stage. These parts rely on one another to operate, so if there is a problem with either part the entire system shuts down.
Panasonic
With Panasonic's patented Twin Guard technology,
2 compressors are completely separated from one another, with no reliance on the other to operate. So if one of them fails, the other is unaffected and your freezer will keep chugging along at ultra-low temperatures.