Dressage with draw reins

In preparation for Inavale (fingers crossed), we rode in draw reins today.  It was 84 out, and Charlie was a bit of a slug again.  I feel bad - I should have him skinnier and in better shape before asking him to work in this heat, but I never expected it would get this hot this early in the season, and the last couple months got away from me.
We worked on 10 meter circles down the centerline, changing direction.  Then we did quarter line to quarter line 10 meter circles.  Wait - those are the same thing.
Then we picked up the canter from the quarter line, which was really, really difficult to do.  John said he expects in warm up, in a big grassy field with no wall, Charlie will kind of ignore my aids and not really pay attention.  So he recommended that kind of precision in picking up the correct canter when it sort of surprises him.
Then we did some lengthening, at both trot and canter.  At first, this was difficult to really get Charlie going, but after the 10 meter circles, we got the most amazing lengthened trot yet, and then some really nice canter as well.
The draw reins really help, although I tend to let them slip.
We also worked on a 10 meter circle on Charlie's bend.  It is asking with the inside leg (next to the girth!) and then at the same time, half halting with the outside hand.  There is also asking him to leg yield to the outside while on the 10 meter circle, except for then the outside hand holds him and he doesn't really leg yield out.
John said it was a bit overdone, so that the show will feel like less.
As we were leaving, he talked a bit about the styles of showing, how 4* horses average competition lifespan is now 2 years, but the average age of an Olympic horse is 17 and it used to be 9.  He said it used to be very difficult to get a 9 in dressage, and then suddenly it got much easier.  He said it is also much more difficult for the horses going advanced and above because they have to have considerable collection for dressage, but then they can't collect like that to get over the cross country fences, so they have to know to listen to the collection for dressage but the same aid means something different for cross country.  It was really interesting.
He said again not to warm up for 15 minutes - to get out there, get immediately to work, and then stop so I don't wear him out.  He said check on how many riders are ahead, because sometimes they get really far behind and in the heat, I do not want to overwarm up Charlie.