Holy shit S3nt0n, I'm on nightshift RIGHT NOW!!?! It's 3:30am and its getting harder to stay awake. Sitting in a control room with a few plant operators, trying to look busy...
Since when did you start eating 'decently'?
I find eating smaller, regular meals throughout the night keeps you awake as your body is keeping busy digesting them. Stay away from pies\sausage rolls etc, as they will give you a big energy boost for a short time, but then you'll come crashing down. Stick to low GI foods (multigrain bread, cereals, muesli bars) and fruit. Plenty of water helps too, have your 2L if you can. If anything, you'll stay awake as you'll be busting for a piss every 5 minutes!
Like wise old SOD sez, nightshift has its perks (no managers, less hassle, camps are quieter), but over here its about 3 degrees at night! Another downside is you don't get to see many people, all your workmates are asleep when you're awake, and vice-versa.
I guess you'll know when enough is enough, and if all else fails you can always get a job at WacArnolds