I ran NYC yesterday - my long runs were 1x 18 and 2 x 20 miles - I was planning a 22 but had to stop at 11 becuase of IT band issues.

My 2 x 20 milers were around 3:15  - I ran NY yesterday in just over 4 hours

My longest run prior to my first marathon was 22 miles. Made it the entire way and felt awesome. That marathon finish time was 4:24:18.

Don

My longest run prior to my first marathon this October was a little under 22 miles, with a total of about 5 runs over 17 miles.  I agree that having not run the full 26 prior to the race was anxiety producing, and actually caused me to go out a little faster than I should have.   I read all over that you should not run your first marathon with a goal time in mind, and in hindsight this is probably good advice.  Just run comfortably, learn all you can from the experience, and don't let the adrenaline get the best of you.    Once you have a few weeks to look back after the race, you will have a much better idea of what worked and what didn't.  I learned that I wished I had stretched myself out a bit more in training, but that's just me.  Just enjoy, and envision yourself crossing that finish line, arms raised.  It can be a pretty overwhelming experience!

My longest runs before my first marathon were:

2 x 21 miles

3 x 20 miles

2 x 19 miles

3 x 18 miles

I ended up running 3:38 (January 2009).  Some accused me of over training - fortunately I didn't get injured!

My 2nd marathon in April 2009 I did 21, 20 and 18 - had to take a week off due tearing a hamstring in a 10k about 8 weeks before the marathon (pretty dumb) - the hamstring was tight before the race and I knew I shouldn't have run, but I was stubborn!  Lesson learned!  I ran a 3:53, mainly due to the 30 mph winds, 70+ deg and humidity in OK City.

For my 3rd marathon in October 2009 I did a 23 mile training fun for the first time.  I think it helped.  I did the 23 miler at 30 seconds above marathon pace.  I also did an 18 miler at marathon pace (not recommended for first marathon) as well as a 21 miler and a coupld of 20 milers.  I ended up running a PR of 3:26 and qualified for Boston.  For the first time I actually felt great at the finish line.  The race conditions were ideal!

Trust your training and enjoy the race.

longest training run: 25.52 miles @ 9:16 pace

Marathon race pace: 7:00

My longest run before my first marathon wasn't very long at all...

But I personally believe it differs from person to person. My longest run before my 1st marathon was 10km(6miles) I wan't following any training program, but I must say I did feel like I was crawling the last 10 km..however I finished in 4:05hr....

It's best to use a training program, I've learnt that the hard way. I use coolrunning.com's training schedules, they work beautifully !