What are optimal settings for Recycling of Application Pools in IIS7 in a shared environment?
you need to cater the settings to your needs, take into account the amount of memory you have and the peak times of usage for your site/web application.
Also take into account the memory usage of your site/web application as if there are memory leaks you might be recycling more often then you think.
Weigh up any leaks against the cost of recycling, as stated above you will lose state variables.