How long will a typical bacterial strain keep in a -80°C freezer?
Richard Lenski's lab at Michigan State university has been doing long-term evolutionary research on E. coli and maintaining a &quot;frozen fossil record&quot; of their experimental populations every 500 generations since 1988. They still periodically release research papers comparing the physiology of evolved and ancestral populations. For example, this recent paper looks at populations collected at 2000, 10000, and 50000 generations. According to this timeline, they used populations frozen over 3 decades ago.
This doesn't guarantee that your specific organism will last that long, but it does show that freezer stocks can remain viable for longer than some research labs will even exist. Most of their protocols are on the website. I've had lunch with Dr. Lenski, and he's a pretty approachable guy. I'm sure if you emailed him with specific questions that aren't covered on the website, he'd try to find an answer for you.
References:
Changes in Cell Size and Shape During 50,000 Generations of Experimental Evolution with Escherichia coli. Nkrumah A. Grant, Ali Abdel Magid, Joshua Franklin, Yann Dufour, Richard E. Lenski, Journal of Bacteriology Mar 2021, JB.00469-20; DOI: 10.1128/JB.00469-20
Lenski Lab homepage: http://myxo.css.msu.edu