Dairy products are products you don't want to mess with. As we all know, leaving dairy products out too long can make them spoil, so what about cooking them slow...as in a slow cooker?
My rule of thumb on this is that I never add dairy products to a crockpot recipe until the last 30 minutes of cooking. Why? Because they can spoil.
Most dairy products are going to be used to make the recipe creamy...but it really won't add much to the taste (there are some, such as: cheese, cream cheese, etc. that do add a flavor, but mostly dairy is added to make your recipe look creamy)...
Since, you are really just going for a creamy look, you don't need to 'cook' the dairy product, you just need to 'melt' it. Products like cheese and cream cheese will melt in 30 minutes time, so why take the chance of them spoiling and cooking them any longer than that?
Dairy, such as: milk, sour cream and other creams shouldn't be added until the last 15 minutes of cooking. Again, they are being added for the 'cream' look not really any big taste factor.
Now, products such as creamed soups can be cooked all day in a crock pot and it won't hurt anything.
Even if I come across a recipe that doesn't tell me to leave the dairy products out, I do any way.
Happy Slow Cooking! Hugs...