Caffine Question?

Is it possible to build up a tolerance to caffine? I just started working third shift and it's hard to get used to when you've only worked first. But I can drink two cups of coffee before bed, and sleep for eight or so hours. I've always been that way. So, have I built up an immunity to it? And if so, is there anything that i can either eat or drink that will deffinately keep me awake?