When I was young...
I wanted to catch 'cab.co.uk' with 123-reg domain watcher system... =)
I desperately waited for the domain to be released and was very disappointed
when 123-reg failed to catch it.
Then I started to learn.. and went to 123 and asked them how often do they query registry?
Surprisingly, I received an answer. Honest answer!

They do query whois 3 times a day!

)
Wow! I immediately sent them money back request =)
Then I went to C.Holland and his dropcatcher and before ordering any credits, inquired how often does he send requests in order to obtain names which I'm after..
C.Holland started to play silly bugger, asking me whether I want to also know his credit card number and bla-bla-bla..
It seemed too stupid for me to use his service if he can't answer question that simple. The answer I wanted to get from him "yes, we run requests as often as possible" (and at that time there was DAC already and I knew how often it could/should be).. But, alas, C. wanted to look too smart (what finally made him look exactly opposite)... as his system now loses hard to me and other competitors.