If you would like Get It Done to put a task in your Today folder (or another Focus Area) every week or so, you just have to set the task to be repeating:

  1. Open a task
  2. Tap on Repeat
  3. Set your repeat pattern (note: there is a "only if last task was completed" checkbox. This can be handy for tasks that you care about when the last one was completed)

See also how to schedule a task to appear in my Today folder.