This isn't something I'd ever thought of making until recently. True, I don't often use sweetened condensed milk (because we generally avoid refined sugar), but last week I needed it for a dessert I was making. And when I discovered I only had a can of condensed milk, I decided to make my own. Note: I found out that sweetened condensed milk can actually be made from scratch, but the recipe I found also says it takes two hours to cook down and I didn't have that kind of time. I made mine from canned milk and raw sugar and it was oh, so tasty.
Homemade (sort of) Sweetened Condensed Milk
12 oz. can condensed milk
1 c. raw sugar
Cook both in saucepan on medium high heat, stirring constantly for 20-30 minutes until mixture is as thick as you want it.
Certainly more time consuming than opening a can of sweetened condensed milk, but a little more healthful. And I like knowing I can make my own in a pinch.