They'll start a drinks service as soon as they're released to move about the cabin, and dinner service will begin shortly therafter. I'd say you'll probably be eating about 60 minutes after takeoff. The whole meal, including dessert/drinks at the end is probably about an hour.
They they'll leave you alone until shortly before landing, where they'll come through with a breakfast. A GOOD crew will ask you at some point after boarding whether or not you wish to be awakened for breakfast. In my experience, the breakfast itself isn't worth the effort or calories but the coffee is welcome, at least until they started serving poo-brew.