Best [Exact] and Broad counts for a keyword? What do you look for?

[Si_P]

Hi,

I have been reading through tons of threads to try and find the best counts that you should look for in keywords, for exact and broad phrases.

I see most look for a minimum of 2000 exact searches and for broad, the higher the better but why is exact only a minimum of 2000??

Any answers would be great. I normally piggie back off product launches so my keywords are a given but now i want to build lists in different niches i need to target the best keywords for those niches and SEO my blogs to the hilt.

Thanks,
Si