Do you keep repeated tasks, such as your lunch-time routines in your GTD task management system such as MonkeyGTD, or in your calendar such as Google Calendar, and WHY?
I decide this based on this rule: Does it matter exactly when I do it?
If no: this is a task which goes into my task list (example: check finances, backup my data). Usually without a due date.
If yes: this goes into the calendar (example: appointments). If some work is required, it also goes into the task list (example: business meeting where some preparation is needed, presentation). I also set a due date for the task so my task management software can sort it on top (I like to do tasks with a "hard due date" first).