In my own experience over the years, it's true it won't keep well. My rule of thumb is if it starts smelling like ammonia, it's too far gone, but I've had it in bottles from men for another two days before feeling it's no longer good. Of course, there are dicussions about possible bacteria forming, etc, but c'mon, if you're drinking other men's piss in the first place, you already know you're on the dicey side of things. 😉
I have been drinking piss left in beer bottles, water bottles, and pint glasses in the bathroom at the bars for quite a few years, and some men have even generously filled a cup or bottle on the patio for me more than a few times. I've never been sick from it other than drinking too much at once - a two-liter bottle of piss isn't meant to be chugged. Finish it over a couple of hours with an occasional bottle of water in between and take a couple of pisses to get it through your system. I've had as much as a gallon of piss in an evening with no issues as long as I pace myself. Though it's hot as fuck to show those around you how thirsty for piss you are and how much you can drink for them, but reality has some limitations.