Well, this might seem like the DUH answer... but your first long run would be about 33 minutes. And your next about 36.3 minutes...
Seriously, there are a number of schools of thought here. The 10% rule generally applies to your WEEKLY mileage, so you're running about 9 miles a week. So you'd probably be okay stretching one of your runs to 4 miles for a couple of weeks, then 5 miles.
Being curious, I checked Runners World's latest 1/2-Marathon training plan as a sample reference. There, they define "long run" as anything at or longer than race distance, run at or below race pace. Specifically, the long runs in their 9-week buildup appear to hit about 33% of the weekly mileage.
So it looks like the rule of thumb would be to:
1
) Add about 10%
(or 1 mile at first
) per week to the total mileage
2
) Keep your "long run" about 1/3
(give or take
) of the total mileage.
Note that as one gets significantly above 10mi/week, this may require adding a fourth and/or fifth running day...
So, pick one of your runs and add a mile. Then add another mile the next week. At about the 4th week, you'll have to add a 4th day of running
(2 miles or so
) to keep rule #2. At some point, though, I think rule #2 goes away. probably at the point where you're running about 9-10 miles
(3 days
) a week in addition to the long run. Just a guess though.
Good luck and watch that ankle!
Perhaps someone who actually knows what they're talking about will weigh in here...
:-
)