I'll let you in on another secret for "going long" successfully, that many people don't talk about, but that can be incredibly important for a good race - or at least, avoiding a very bad race. Imodium. It's a Godsend, and one of my essentials for marathons. Yep, every marathon, and any half marathon or triathlon where I'm going for time.
You see, many of us have a funny reaction to working hard in the heat for long periods of time. For whatever reason, fluids start to accumulate in our lower gastrointestinal tract. The results after 2 to 3 hours of this activity are uncomfortable, crampy, distressing, potentially dehydrating, and wreak havoc with your finishing time. (If you have never experienced this issue while running for a long time in the heat, well, just skip this whole post and forget that I said anything. Some people don't get this. You'll know it when it happens.)
Remember that hydration, sodium replenishment, refueling, and managing our digestive tract issues may be even more important for us slower athletes who are out there on the course a long time. Many of the really fast people are off the course and eating post-race goodies long before they experience the problems that many of us slower folks experience. Those fast folks are often the ones that turn into coaches, too, so they often don't know anything about managing the problems of people who are out on the course for hours and hours and hours, and often don't advise them well on these aspects of successful completion of the event.
The Imodium label warning says: "2 caplets (with 4-8oz of water) after the first loose stool; 1 caplet (with 4-8oz of water) after each subsequent loose stool; but no more than 4 caplets in 24 hours".
Well, I'm not going to tell anyone not to follow the label directions to the letter. But I'll tell you what I do. I know I'm doing to have very very loose stool without them, so I just take them pre-emptively. I do this, for events lasting 2-3 hours or more: Two caplets as soon as I wake up, first thing in the morning (which is sometime between 4AM and 6AM for big races). Two more caplets as close to the start as I can take them (usually some time between 7AM and 8AM).
That totally solves the problem for me. Less dosage than that doesn't do the trick, and earlier/later doesn't seem to work well either. I haven't experienced any adverse reactions from this regimen, except possibly some abdominal cramping when I stopped running. And no, it doesn't turn everything to concrete. Just so you know. :-) It also means I don't have to be quite as particular and superstitious about what I eat the day before the big event, because I don't have the digestive problems that I once attributed to bad pre-race foods.
I'd tell you from whom I learned this regimen, but I'll just let her chime in herself.