Generally, the lower the refresh rate, the less you should AB (if you want to look legit to TNT).
For example: if your refresh rate is 8s, AB 1-2 hours a day.
No (sane) person is going to sit at their computer for 24H, refreshing every 8s.
If you decide to AB for long periods (preferably with a longer refresh rate), remember that people need to eat, sleep, and take washroom breaks, so you should make a schedule (in the schedule tab--it's really handy!) .. or you could manually start and stop the AB'er.
Make sure your refresh rate has a good / long range (like, 8s-30s) because it looks more legit than someone who refreshes (exactly) every 8s