Actually, it is a really good idea, and a lot of groups do this all over the forum. It actually helps keep things easier to find in each section of the forum as well-because when you are on the main page of this section of the forum there are not so many threads going at the same time. When there are weekly threads, rather than daily ones, and only one thread going per individual topic (like posting your exercise, or a recipes thread) it makes things much cleaner and easier to find for new people coming to the forum.
A lot of times weekly threads are started on a Sunday or Monday, and they work very well here. Laurie, since you are a group leader, if you start the weekly thread you have the ability to close the thread at the end of the week. If someone else starts the weekly thread, then I can come in and close it when the new weekly thread is started.
Weekly threads are really not all that confusing. Some of the threads I am involved with actually have monthly ones even.
Having a weekly thread rather than a daily one, also helps Laurie and I have less threads to close.