From a 2012 episode of Student of the Gun TV Show on the Sportsman Channel.
Max Michel was being interviewed and made the following statements
“It’s a big misconception (that dryfiring is only for beginners).”
“I’ve been shooting competetively for 20 years...and I still dryfire a minimum of 30 minutes a day for 5 to 6 days a week.”
“Dryfire at about 50% speed. ... If you dryfire at half speed it allows you to talk yourself through the technique.”
He comments that speed will come with adrenaline and necessity but training should be done deliberately to reinforce proper technique.
He goes so far as to suggest spending a third of your range time dryfiring. Making sure that your technique is correct before you start burning ammunition.
I thought the statement below was amusing. A lot of folks think that professional shooters get good because they can shoot a lot using the ammo their sponsors provide them. While I'm sure it helps with training, people don't become pro shooters until they're already very good and they get good on their own nickel, because that's all they've got until they get good enough to turn pro.
“When you buy a million rounds and put them downrange and you do pretty good, maybe somebody will give you a million more later.”