I think you summed it up nicely Brad ... If it's down nice and not lifting etc. then it's a good thing as there's no way the PF artwork can get wear  .... BUT ... if it lifts ,bubbles etc. then it can be bad .. VERY BAD ..  .

I agree with you in that I would only ever attempt to remove mylar unless it was absolutely necessary ( just the thought of trying to get it off scares the shit outa me .  )