I live alone and buy milk in gallon jugs finding that if I shake the jug every day I can go a week or two beyond the date. I just checked the jug I finished yesterday, the date was April 5 but that's a sell by date.
I hesitate to mix the milk and air as every time some milk is poured out, room air with its normal bacteria flows in and replaces that amount of milk, so I prefer the air to stay above the milk. Actually, I go by that theory with every liquid I use out of a container as I also use things slowly... same used bottle of ketchup, mayonaisse, mustard, lemon juice, cooking oil, wine, etc. may be around for months or years... 2 liter soda pop a week or two...