Is it better to run 3 ten mile runs with food breaks or one 24-26 mile run when training for a marathon?
How would this translate to a race time?
In my opinion the furthest I would go in training pre marathon is about 22 miles. And I would only do 1 of these. The rest of the long runs I would suggest should be between 18-20 miles.
The reason I say this, is that running the full 26 miles takes a lot out of you, and I think would have a negative affect on the actual marathon rather than a positive.
I think a 22 is okay, as it's in the last few miles that you would hit the wall(if you were going to). You definitely don't want this to happen in training. Doing a 22 will give you the confidence that you can do the distance, which is why I would suggest you do one.
I can't see any reason for doing 3 x's 10 miles. Do you really have the time to do that in one day?
Also, a reason for not doing 3 x 10 is that when you do the very long runs your body has to learn to use fat as fuel. If you do 3 x's 10 you wouldn't get this benefit.
I hope that helps.
Btw I don't understand the last bit of your question - how does this translate to race time?
Each one would have a different effect on fitness, but in theory both would be good options.
One long 24-26 mile run would help ensure you go the distance on race day. Three ten mile runs with breaks would allow you to run at a slightly faster training pace for the overall mileage.
It really depends on what your marathon goals are (i.e. crossing the finish line, setting a PR, etc.)
If you want to drop your time, the main thing is to spend time at marathon pace. One of the best marathon training runs I know of is a 20+ mile run with the first half easy and the second half at marathon goal pace.