Acurite 2032C Display Battery Life On Battery Power..

I can’t seem to find this anywhere so maybe one of you guys have an answer.

On my 2032C recently I had a power outage that lasted several hours. I was on generator power almost all of the time.
After my power was restored the next day I noticed WD receiving the wrong weather like temp etc…

Then I tracked the problem down to my Acurite display which had defaulted to the factory settings so once I reset it everything was back to normal…

The backup batteries were only a few months old.

I would like to know, just how long the batteries will power the display unit without power.

Thanks…