http://www.runnersworld.co.uk/forum/beginners/training-for-the-right-distance/166481.html
Hope the above advice helps.
There are too many theories and tons of information regarding training that it's best just to keep it simple.
As you have plenty of time to train before your half marathon, a good plan would be to build up your base mileage with 3 or 4 runs over the week. Once you are comfortable with your base mileage you can start doing some speed work. There are a number of different speed sessions that you can do. All involve running shorter or much shorter distances at faster paces. You'll find phrases like tempo, fartlek, intervals, HITT bandied about.
Generally you would be running one long run per week at a slow pace. This run would take you upto and possibly beyond your race distance. You would also do one other run at a similar pace of about half to 2 thirds the distance of your long run. A third run of a similar distance to your second run, either at a faster but steady pace or as a tempo run. Then speed work - fartlek; intervals; hill reps; HITT etc. All manner of speed sessions.
Your long run helps build stamina. You need more than stamina to race, you need to be able to run at a faster than training pace for the distance of the race. The speed work helps you do this.
So yes, in the first instance you are right, you need a good base mileage upon which to work. However there comes a\point where you can not do a long run every time you head out the door. At this point in order to gain most benefit from your training you need to add some speed work.
One long run a week is enough to build endurance.
