Sour cream and cottage cheese have a short shelf life, usually 7-10 days after being opened. But if you want to store one of them for longer, then all you need to do is invert the container and keep it in the fridge, says the One Pot Chef.
It sounds ridiculous but what happens is that you create a vacuum at the top of the container and it helps to reduce the bacterial growth so it doesn't go off as quickly. Just make sure you have a tight-fitting lid or you could end up with a bit of a mess.
He also recommends that you can buy items like margarine or butter in bulk and freeze them, where they last for up to six months. To protect paper or foil wrappers from frost, wrap them in plastic wrap/plastic film first. Defrost and you're good to go.
Quick Tips: Dairy Money Savers [The One Pot Chef]