there's nothing wrong with your plan, however...
I don't like going into a mileage build with a preset idea of how much I will increase my mileage. It goes up as it goes up....meaning since I don't know how I will feel as the increase happens, I don't like to try to hit certain targets. and if I need to pull back, I do.
my goals are instead:
1) take a day or 1/2 day off whenever it is needed (when getting really tired etc.) because just running through it day after day is not good training
2) continue to do some quality workouts (but not expecting much since I may be tired) still I will be getting faster as I get stronger.
I am currently adding doubles. So for me, it usually goes something like this:
day 1 - 1st run (8-10 miles) usually a workout
day 1 - 2nd run (12 miles)
day 2 - 1st run (8-10 miles)
day 2 - rest
something like that: 3 runs then a rest. The mileage totals will be whatever they will be and I am trying to not think/worry too much about it. Instead just focusing on getting stronger and adapting to the mileage. When I feel particularly good, I go longer on one of these - like 14-15. That's how I build my mileage.
week 1 - 88 miles
week 2 - 82 miles
It just turned out that I ran fewer miles in week 2, big deal. I felt I needed a little more rest and now I start this week fresher and ready to hit 100 possibly or not. It will be whatever it will be. My previous weekly totals were about 4 weeks in the mid 60's. I think the only reason I can bump my miles up this much this quickly is because I take those 1/2 days or full days off when needed. I think this is really important.