Fresh dairy products: a general rule of thumb is, the higher the fat content, the longer the shelf life, both before and after opening. Aged cheeses are a bit different because of they have a lower water content.

So, cream will keep longer than whole milk, which keeps longer than skim milk. Full-fat sour cream will keep longer than the low-fat products, which have all kinds of modified starch and sugar added to make up for the missing fat.

In general, I find heavy cream, cream cheese and sour cream will keep for up to a week after opening. Cottage cheese isn't quite such a good keeper, maybe 4 or 5 days tops.

Doreen