I have run three marathons. I can tell you that the pain of the last hour is something that you try to forget.
I have my inaugural half on November 10. Hoping to break 2 hours, but a more realistic time might be 2:10 based on my 15K performance back in April.
Even at 53 years of age, I'm still relatively new to this running thing (I have about 15 months experience). I'm still getting faster, but I also recognize that old age will eventually surpass 'beginners' gains' and my monthly PRs will stop.