I've been testing 2 campaigns for 2 weeks, I broke even, but didn't profit. This time I tested them more or less properly: I compared this week's data to the previous one (earlier I just did Tuesday vs Monday, Wednesday vs Tuesday, etc.). I had more conversions on Thursday and Friday, but I have no idea why. Probably by the end of the week people thought that it was about time they solved some of their problems.
I was also split-testing two ads per ad group from the very beginning: if the commercial intent of the KW was pretty low, then no matter how enticing the ad copy was, clicks and conversions were low or non-existent. Though this time I had fewer KWs that would attract people in the "browser" mode. On the other hand, even if the KWs seemed to be of high commercial intent level, CR would sometimes be low.
By the way, sometimes I read on other forums that higher CTR would result in higher CR, but in my tests this wasn't the case: high-CTR KWs would sometimes have low CR, and the other way around. So as you can see, there isn't much consistency in the results. Moreover these results in part contradict the ones I've had before. I guess it all depends on the niche and offer.