I seem to remember Bryan writing that protein synthesis goes up by 50 percent after 4 hours, is at its highest 24 hours after a workout, and drops back to baseline after 36 hours. So I'd think that 24 hours after the workout you should have plenty of protein in your system. Ie, if you work out at 5 pm Monday, you should get a lot of protein in your system by 5 pm Tuesday, and worry less about getting protein late Tuesday night.