In reply to dinodinosaur:
Yes, though it should be said that this probably happens less than the reverse! It should also be noted that return matches on these routes have sometimes been a bit of a shock.
Early examples as a schoolboy were ascents of Undercracker (a very early E1 for me) where it just completely flowed. I think this was a reflection of having being working through the Avon Gorge HVS's as I'd moved to Bristol and some of these (Beard of Ffoeg Nosam for example) have since had significant upgrades (and were desperate). I also did Nightride at about this time, which has a reputation at E1 and for which balancing up Avon routes is not particularly good preparation! Again, it went smoothly though I remember running it out up the strenuous bit.
Turned up at Queer Street in mid-summer 1986 or 7 and made a last second decision to try my new shoes (Fires) that had arrived that day. I had to squeeze in and they required a very different style than my clunky Cragratz, but the route went easily once I had sorted out the gear. Apparently, this isn't a common experience on Queer Street. I should go back to it at some point for a spanking!
Lastly, on my first visit to Staden the place was absolutely rammed with a lot of queuing for routes. Hard to believe these days. We sort of 'did' the crag - about ten classic routes - one after another and it all seemed easy. Particularly Cathy's Clown (then given E3) which I led and reported down as 'probably only E1'. Subsequent parties that day found it anything but! I went to 'whip up this' again a year later in less than ideal conditions and made it by the skin of my teeth!