How long do I keep doing something that isn’t working?

I’m posting very frequently on social media to try to build my audience with the idea of building my email list, with the idea of selling more copies of my book and future products.

The problem is I’m getting very little engagement so far. Granted it’s only been about 2 weeks, but given that time is limited, I’m trying to think strategically here. I understand that massive action means taking action until you get the desired result, but I don’t want it to wind up being a year from now and I’ve put dozens of hours into Instagram with nothing to show for it.

How do I know when to pivot vs keep going even when there’s no evidence that it will work?