I was told by an eHarmony rep that using the "find matches" button actually reduces your chances of being matched, because it overrides the system's 24 hour search, and the system is often times not likely to do a thorough matching process in the minute or so that it takes to do the "find matches" search.
Thats not true for me. I get 7-9 a day regardless of how many times I hit that button.