Since I have an informational site, I have my bounce metrics set differently than the default GA setting. I measure bounce by whether they stay 90 seconds. If less than 90 second, then it is a bounce. Or if they click through to something else before 90 seconds then it is not a bounce. That being said, I have a very low bounce rate that ranges between 22% and 27% and an average time on site of just under 4 minutes. During this time I do see an increase of my bounce rate of a couple of percentage points.