The GTD setup guides advise against using start/defer dates that a lot of task manager apps have. If an action cannot be started until a specific date, the guides and the book state that these should go on your calendar. However, if those tasks are recurring and you forget to reschedule them, they can be missed for future instances. Obviously, the weekly review should pick up these omissions but it seems like extra work that could be left to the software. What does everyone else do?