The short answer is as many times as you want, you’re not going to hurt yourself under most cases.
The long answer is that your body can’t process that many changes. So really I would limit to an hour, maximum an hour and a half, a day.
But the real indicator is how you are feeling. Because if you are starting to get overwhelmed or desensitized, like you can’t even tell that anything is working anymore, then shut it down.
Or if you start to feel really tired and you just need to lay down and relax or you feel like you just don’t want to do it anymore. Those are big indicators that you’ve had enough and there’s always tomorrow. So just stop when you feel like you need to stop.
And that is how many times a day you can tap.
How do you choose your topic in EFT tapping? Check out this article.