Would just like to address this while I'm at it:
Oh come off it! Re-arresting someone is hardly difficult. As for "requiring new evidence" - if you didn't have enough to charge them in the first place, then odds are you'll have new evidence when you re-arrest them because you'll have managed to piece a case together.
I really don't see why the Police should be able to place restrictions on a person's liberty in the longer term, it's extrajudicial punishment IMO - especially if the Police 'NFA' the case further down the line.