[Plugin: W3 Total Cache] Simple Setup Question: CHMOD'ing in MU

Hi there, I am setting a WordPress MU network and
using this plugin for speed. My question is…

When CHMOD’ing temp 777 on the /wp-content/
and /uploads/ folder…

After I do a single site activation for the primary
network’s site… do I have to temp 777 those folders
everytime I setup a new site and “activate” the plugin?

Or is ok just to temp 777 once, at the time of install
and that action serves for all other sites/blogs that
get added on later.

Thanks!