Cream tends to separate once it has been frozen and is never as good as it was. Yoghurt is fine - I freeze it all the time for the kids. I haven't ever frozen sour cream though. I live out of town, so I can't go to the shops to buy cream if I need it for cooking, so I buy the long life cream to have in the cupboard and it is just as good as fresh - especially for cooking and if you need to whip it, just pop it in the fridge to chill first. I find the long life cream straight out of the cupboard is particularly great for cooking as it is less likely to curdle if you are adding it to a sauce or to a dish because it isn't cold already.