I've been doing HR training for a few months now and it's definitely helped me pace myself better. It's not a magic bullet, but it's a useful tool to have in your arsenal. Don't expect miracles, but it can help you optimize your effort.
I've tried both, but I'm too lazy to create my own plans. I need someone to tell me what to do, otherwise I'll just slack off. Coaches keep me accountable, even if they can be pricey.
Stairs are the worst, mountains are insane.