After a 6-mile run and an 8-mile run it makes sense to reduce the distance a little before you increase your distance again.
I would get a new pair of running shoes as soon as possible if I were you. A pair of good running shoes will make your running more comfortable and reduce the chance of injuries.
I purchased two pairs of running shoes last year and plan to order another two pairs soon. I usually use one pair for the weekdays and the other pair for the weekend long run.
You can check amazon.com on customers' reviews or running world's web site for tips of selecting runnig shoes. I ordered ASICS GT-2150 last which fit me well for I'm a normal type of runner. See for information http://www.amazon.com/s/ref=nb_*****_noss?url=search-alias%3Dsporting&field-keywords=accis+gt+2150
Note that you don't have to pick the lastest models which are generally more expensive.
I have started to run both days in the weekend since last week.
I ran about 16 miles totally this weekend.
