low limit expected profit

I've played 2-4 limit holdem about 15 to 20 times or so in a casino. I've only kept records for the first dozen. I had'nt gone for a while, then started back casually wich is why the record keeping had slipped. I dont consider the recorded 12 times enough to get an accurate average, but I averaged about $12/hour playing about 5 to 15 hours per game. I thought this was very high for a 2-4 game and now I'm about break even or down every time I played since then.
Am I expecting too much from a 2-4?
Has my expectation been skewed because of a lucky run of twelve games?
I feel that I dont have a standard to judge by to know how I'm playing.
So my main quetion is, what kind of average can I expect from a 2-4 limit game, and whats an average I should expect to swing up or down before I can consider it my play and not luck?
thanks