I am new to this recipe and I love it. Could I substitute the milk for water? I am concerned about leaving the cake out for too long since there was milk in the frosting. Anyone?

And also, I love this frosting and have made it a couple of time but is this right?
3 teaspoons clear vanilla extract
5-6 tablespoons of milk (cold)
(this is in the recipe section)
this is too much liquid for this recipe, I have been cutting the milk in half and the consistency of my frosting is still very thin.
**2lb bag of confectioners sugar is 4 cups, right?**

I use this recipe too. You can use milk or water. The amount of milk is so small it's not a problem sitting out. The large amount of sugar acts as a preservative...no worries. I use milk and let it sit out for days, even over a week at room temp and it's not a problem. And yes, I only add about half the milk also. The full 5-6 Tbls is way too much in this recipe.

a 2 lb bag of ps is 7 - 8 cups.

7 to 8 cups? guess that's the problem, I was adding too little sugar.

I use a 2 lb bag of sugar and still only about half the milk.

You don't use any butter or shortening?

Sugar is hygroscopic (water absorbing) so it controls the water activity of liquid ingredients used in your American b/c recipe. (Will only work when amount of liquid is small and amount of sugar is large.)

Water activity & microbial growth:
(Prolonging Bakery Product Life.)

http://tinyurl.com/6fbkcz

WJ Scott in 1953 first established that it was water activity, not water content that correlated with bacterial growth:

http://tinyurl.com/bmsato

Formulating for increased shelf life:
(Decreasing water activity results in hostile environment for bacteria.)

http://tinyurl.com/csu2b9

HTH