As a coffee shop owner of almost 7 years, here’s the answer!!
If it’s crazy busy, like on a weekend and the lines out the door, definitely limit yourself.. 30mins feels like the sweet spot. Any other day of the week, please sit down and enjoy yourself forever! All day even! as long as you bought something and aren’t taking a seat away from someone who really needs it, we certainly don’t care. Especially if it’s art, we love that. People on computers doing zoom calls though, those suck haha.