Just wanted to say that the training plans in my last post are on that link I attached.
I don't think of the first plan as "low mileage", but the dividing line seems to be a consistent 55 mile week (at least according to P.Pfitzinger). Not all half marathoners run 40 miles a week, but from my experience (very limited...not a coach...only been running hard for 2 years), I have to say that going over the race distance in training improves performance in the half- even if you don't get in the 40/week. Any week should have a reasonable balance between midweek miles and long run distances.
I tend to do more midweek mileage and can pull it off. I have had my share of issues when making increases, though (calf strain, achilles tendonitis) and had to reduce for a while and then hold steady before the next jump up. Currently, NO ISSUES. Praise God!
Always be careful when increasing weekly mileage or speedwork :) (Duh! Like you haven't heard that one before!!!)