This is true, except:
1) You're most likely going to crash in a race, not a training ride. In 12,000mi I've never even seen a dude crash, except in races
and
2) proper valve extenders work exactly like a regular valve, threads and all. No more of a hassle than normal.
Training ride, albeit a fast one. Someone just posted this recently (not me):
Less intense training ride.
Granted, I've seen a lot of crashes in races. However I've seen a lot of crashes on training rides as well. My last crash was on a training ride. In my first 5 years of racing I crashed only in training.
On valve extenders... if something has to go it might be that. I've chosen, for the last few times I rode outside, not to use the aero clinchers simply because it would be one more thing I had to get before I headed out. The race wheels I'm committed to using. The aero clinchers not so much. But you're right, properly set up an aero clincher shouldn't be any more of a pain than a non-aero clincher.