Two is enough to be really aggravating. I believe an easy, non obvious, way to let tyres down is to put two bits of match stick into the valve and loosely put the cap back on. Though anyone with any nous will spot the bits when they come to pump 'em back up. Of course it is obviously a deliberate action and if happening fairly often pretty annoying. How long would it take to pump up 4 tyres with a footpump, maybe that 6 AM beep would be a less annoying 7 AM beep...
If you have a valve removal tool...