Casein is the slowest moving protein. It digests around 8 hours. As far as carbs go, it depends what you're doing. It's better to stay away from complex/low glycemic carbs in the few hours before you go to bed because they take so long to digest (during the daytime they're the carbs you WANT to take though) if you're trying to burn fat. Given that your goal is to maintain weight, though, you should be fine. Eat mostly high glycemic/simple carbs post-workout and later ion the day.
And again, the protein part is very important. To maintain your current muscle mass if you weigh 200 lbs, you need 200 grams of protein a day. If you want to gain any more, you'll probably need to go well over 200 grams occasionally on days you lift.
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