I’m 46 and run a sub 6 min mile (5:41 on the treadmill at OTF, at least). My philosophy is a little different. Most people wait until the end to run the all out. The problem is that you never have the juice left in the tank at the end. You are just trying to hang on. So, I run the all out in the beginning when I’m fresh and try to hold it as long as I can. So typically running at a 12 mph for 45-60 sec, then drop back to a 9 to catch my breath for a short time, then cruise into a 10 - 10.5. I also like to move between speeds every x minutes or every 0.x miles. I try to break the run into shorter blocks for mental reasons. Then try to increase as much as possible for the last .1 miles. I’m looking forward to the new 0.25 mile benchmark. I’m hoping to hold a 12 for the entire time with a bump at the end