How Long is Battery Effective Life

Hi,I have a Ring 3 plus doorbell that I got in Oct 2020, along with a spare battery. I have always charged the spare and have it ready to replace the battery in use. Typically, I have gotten about a month of service before I had to swap batteries Lately, however, that is no longer the case-- seems like I have to swap out about every 10 days -- and I don't get notified, I just discover that doorbell has gone off line.Is it the battery or something else?Would appreciate assistance Thanks