In reply to Ramblin dave:
It's only really an issue if you are climbing with absolute beginners who don't have the cheating 'skills' to pull past a move they can't do, and get to the point where they just want to come down.
If you are talking about someone who onsights 6b having a play on a 7a, say, then there will be very very few routes that you can't get to the top of with a bit of creative thinking - most moves should go if you have a bit of a rest first, say, or failing that - rope tension through a hard move, 'the assisted dyno!', using bolts as footholds, or if all else fails pulling up on a draw or on the rope. To be honest on Portland if you are a competent climber and you are not sure you are going to make it to the top, it's probably better to try it on lead as you can always thread a staple mid way when you want to bail.