QUOTE(Mary Kuch-Nagle @ Jul 12 2010, 09:26 AM)

I missed the half marathon benchmark due to being out of town, and as a result Saturday's 25K was pretty rough. I got to about 12 miles or so and then ended up walking most of the rest of the way. Should I take another try at it this weekend to get the longer distance in - just so I'm prepared for the upcoming 30K on August 7? I don't want to over train, but I do want to keep up and on track. Thanks.
Mary,
Look at it this way... You got to 80% of the distance, and the remaining 20% wasn't so good. But...not so bad that you couldn't finish it. Funny thing is, if you compare it to a marathon, 80% puts you right at the 21 mile mark. The running world is full of stories that start out,
"I was doing great until I hit that 21 mile mark and I knew I only had a 10K left, but the wheels fell off." 
It's not recommended that you try to go out and make up miles, so my suggestion would be
not to try again this weekend. I would have you follow the schedule as planned leading up to the 18.6 Benchmark.
Here's how I see your situation: You already know why it didn't go so well for you,
"...due to being out of town..." and that's a valid excuse. Sometimes life throws us a curve. If you can get your head around making the best of the mileage in the upcoming weeks, you should be mentally prepared for the 18.6 benchmark. Next weekend (8/24-8/25) we're right back up at 13 miles again. Go into it with the attitude that's it going to be a training run/walk that you will do within your ability, and do everything you can to make it go well, ie; POSITIVE. This includes fueling, hydration, clothing and most of all, attitude. Remember, you've completed the 15 mile distance, and you
CAN do this.
We all have bad days. Over training just makes them worse.
Doug