How long should you wait before force shutting down your mac in case of a stuck upgrade/update? Its been a while since my macbook pro started updating, and it is stuck. 

Wondering if I should shut it down or leave it a bit longer? 

The progress bar is stuck and there is no remaining calculated ( calculating time remaining ... )
I would wait as long as possible. When you force shut down a computer that’s in the middle of an update, you’re likely going to have to do recovery and reinstall the OS. I did hear of one case where that wasn’t necessary, but usually that’s the case.