After 8 batches of partial grain brews, I am anxious to try my hand at all grain brewing. I have a big enough pot for a full boil. My question has to do with cooling my wort. In the past, with partial grain recipes, I have chilled by adding 1-2 gallons of chilled H2O to my carboy before adding the boiling wort and then using an ice bath to bring it down to the proper pitching temp. I have been advised that with a full grain boil, however, a wort chiller will be necessary to bring the temp. down quickly. Not that I'm a cheapskate or anything, but is that $50 - $100 really necessary? What if during the last ten minutes of my boil, I kept a lid on the brew pot, turned off the heat and just let it sit until it cooled to the ambient temp. i.e. 70-80 degrees F? Is there something else going on in a quick cool down that is important and that I would be missing?