This can be done for up to 20 minutes at a time and may also be a reasonably good speed to do some mile repeats at. They both have good programs and a reasonably good approach to training. Daniel's has formulas to determine what your pace speed should be for training. Hal Higdon's website has some good marathon training programs. Side Stitches are a little different, but the information is related and is included to be comprehensive.
Side stitches are pains that occur usually just under the ribs when running.
It seems that an unconditioned diaphragm is the cause of this pain more often than not. Either running a greater distance than usual or at a faster pace than usual will bring this pain on. The diaphragm is a muscle that separates the chest cavity from the abdomen. It moves down when you inhale and moves up when you exhale. Side stitches seem to occur most often on the right side of the body.