If the vent is semi clogged, it may take a long while for the pull of the carburetor to create enough vacuum that it can't draw anymore fuel. But with the semi clog, it loses some vacuum, which let's you start it again.
It will run all day at idle because at idle the vent can keep up.
Here's a whole 'nother idea. This happened to me. Had an engine that would run a while but not under load. No load it would run and run. Turned out, after going crazy, that the rubber Seat in this Briggs engine slid down on the carburator a little bit. This caused the needle to shut off fuel with very little fuel in the bowl. The heavy fuel draw, while under load, would run the bowl out of gas.
Another trouble shooting nightmare... Similar scenario. Start up mower in the morning, it would run for 3 minutes then stall out. Wait a minute, start up again, it would run for 30 seconds, like clockwork. Start again, stalls in 30 seconds. The rubber seat in that Briggs engine got deformed from way old gas working on it. The hole, in the Seat for the gas flow was distorted allowing very little gas to flow. The first startup of the day, mower had a full carburetor bowl. after that, gas dribbled in so slow, I could only get 30 seconds put of it.
Check Carburetor Seat if it's a rubber type pressed into the carburetor body