Best case senario for using keepalive_timeout

Hi, I got nginx 0.6.35 with php-fpm and a tomcat. Im using in some
vhosts keepalive_timeout 0 and in some 2 or 4. Now I’m not sure how good
of an idea is it and also not sure in which case I should use
keepalive_timeout or not, I mean which would work the best, static
websites keepalive_timeout on and dynamic off.

Could anyone give some good example, like wordpress blogs or photo
gallery or in Joomla usage and so on.

Thanks!