the way i see it, with how much assembly lube i use on the engines that i build, it could run quite a while without oil before causing damage. all the 22Rs i've put together cranked and cranked with no plugs and i could never get the light to go out, but as soon as i put the plugs in and got it to pop, it would go out. this is with the oil pump primed as well.

just about the same thing happens when it sits as well, especially if you use a lesser quality filter. assembly lube is stickier than motor oil, so it can't be too much worse than a regular dry start.