You can keep them on there as long as you wish. Though they will rot at some point and go mushy. But i like to pick mine just when theres barley any green left and left them sit on a counter for a day or 2 then do to them whatever i need them for. But 3 days will be fine. I think around a week after ripening is when they start to slowly go mushy
I had a few purples I left on the plant and they started getting squishy after 2 weeks. Not rotting, but definitely on their way to losing structural integrity.