I completely disagree. People generally learn more, and develop their understanding/thinking skills as time passes. Saying 'no resits' is saying that people aren't allowed to progress from the stage they happen to be at when an exam takes place.
In addition to this, even assuming that the above didn't apply, with the system slowly changing to one where a single exam determines the result of several years work, to not allow resits would be to put people's entire lives down to how they happen to feel, be health wise etc on one particular day. Yes, sometimes in life we don't have second chances, but generally in life we don't have to recall many years work from memory and convey it all on paper within three hours...
xxx