I do not know. I have been afraid to change system defaults for fear of screwing things up royal. For instance, it is nice to have 60 minutes automatically added on to sports events by default. But, I do change that time for auto racing since auto racing runs on distance or time, whichever comes first.
One default that I would like to change is the record "all episodes" factory setting.
I will not post the link here, but if you google "722 tips and tricks" you will find a handy user made owners manual on a competitors forum. The posters on this former are more informed. And this site has uplink news - meaning you find out when channels go live here rather than stumbling on them by chance.