colder and wiser wrote:
Don't keep bumping it up every week. Now that you're at 8 miles, just hold it there for a while, or even back off a bit if you have a big race coming up or feel more tired or closer to injury than usual. After the season ends, though, you can experiment with going up to 10 if you want, and running some higher mileage during the week, in the gap between XC and spring track.
But your basic instinct to run some more on your own is absolutely correct, and in the medium-to-long term will make you a much better runner. Good luck with the breakout track season.
In addition to this very good advice, let me add that it is a common mistake to think that you always need to add more. It is usually better to get to a certain level, as you appear to have, and stay there for awhile. This is how you build strength of the running sort.
Over the winter, maybe work up to 10 as suggested above. At 8:30 pace, that's an 85 minute run, which is right about where long runs should be for most people racing 1500 to 5-10k. Stay there most weeks, and consistency plus growth in your case will have its effect, and you'll probably be running closer to 8:00 pace by spring, without trying to force the pace.