Here's another chart from Inogen on battery life on a setting of 2 for each of their models.

Wow. I guess it depends on the setting and what model you have.

I have a g4, 3 double batteries and 1 single. The double only last about 3 hours on setting 2. I have had the batteries for 2-3 years.

As batteries get older, they will hold less of a charge. As an example, this is a 4-year-old battery, and it still gets pretty good time. I have 3 of the large 16 cell batteries that I rotate.

Here's a chart by Inogen