I think I understand what you are asking now, it wouldn't create any extra load by storing the default of a board in the boards table. I guess that is just more fine tuning than what I had thought would be a good start. Honestly, if your forum has moderate traffic if you set the default to show all posts it's not going to make that big of difference. What this is really meant for is for large forums that hammer the SQL server heavily, thats where they have very active forums so setting for only new posts within the last week will still show plenty of new posts for them.
Not saying no it can't be done or that I won't do it. This would just fall into an upgrade when I'm working on the admin section again.
