What the other guys just said is exactly right. You did well my man. Legs cramp up on some days... could be a million things. I'm only 36 and my legs cramp on just about every run. The chances of something going wrong over 26 miles is great. You handled it well and still produced a great time for your age. You rush back and run another competitive marathon too soon, you will likely do worse. Your legs will suffer. Take 2 weeks to recover, then start back with 25-30m/wk and work your way back up in mileage. The very earliest I would do another marathon would be mid-January.My second marathon I ran 3:08 at Big Sur Marathon and I wasn't content with the time as I just missed Boston Qualifying. I rushed back and my times suffered because I never really fully healed.Running long distance takes discipline. Sometimes discipline involves running when you don't want to and sometimes it even involves not running when you do want to.