To get a marathon PB should I front-load or aim for a steady pace’?
Most experts agree it's best to either run the first part marginally slower, then try to pick up, or run a consistent pace. Frontloading is too risky. You would need to be able to maintain a very similar pace later in the race and only slow slightly, but your slow-twitch muscle fibres fatigue during the race, causing recruitment of less efficient fast-twitch fibres.
If you run too fast in the first 15 miles, you could easily exceed your lactate threshold, which means you’ll be producing lactate too quickly for your body to clear it. This lactate rise in your muscles will cause you to slow down. Your glycogen stores will also be used up more rapidly. Know your threshold pace so you’re able to run at a speed that is sustainable for the distance. Listen to your body’s feedback during the race, too.