At a glance I thought you said 16 sales a day and I thought that doesn't sound too bad
I usually just watch the total clickthrus. If there's no dip in the clickthrus, then I assume my traffic level is normal.
As long as you're averaging around 1:1000, I wouldn't worry about it, I just build more stuff.
Also, spread things out a bit and it's easier to weather the lousy conversions when one sponsor is underperforming.
Bottom line: Build enough sites to minimize luck and you'll see enough sales/day to keep a smile on your face
