Now i run my rigs for about 6-8 hours last night with BTC Guild pool with total of 4.78 TH/s but i only made 0.01590032 BTC. Now at that speed i expected a little more earnings.
4.78 TH/s at current diff are 0.05408 BTC per day(24h) or 1.5 BTC a month.
So your 0.0159 perfectly fits to your 6-8 hours mining.