I normally put strained whey after making ricotta in plastic jugs that are just washed and rinsed and keep it in a fridge for a week mixing it with the feed for my piggies and it lasts this long without a change in taste, developing gas, mold or anything like that. I'm guessing if I boiled it again after the straining and put it in sterile glass jars - canning it basically - it would last for months and even longer in a fridge.