I would expect that the limit imposed by the supply of cooling water would be very close to that imposed by the supply of air, or by any other consumable. If you still have plenty of air left when your water runs out, then your air weighs more than it needs to, and you can save weight by cutting it without impacting the mission. They might have had slightly more air than that, since the consequences of running out of air are more immediate than running out of coolant, but I can’t imagine it’d be very much more.