Well as a good rule of thumb you should only increase your mileage by 10% each week, during the aerobic phase. This means only easy running, and on occasion you should take a week of rest every couple of weeks by dropping the mileage a little bit. And once you're done with the aerobic phase, which is probably just another 6-8 weeks for you, you should not increase your mileage any further, but instead keep it around the same or decrease it a little bit as you increase the intensity of your training. If you"re at 40mpw right now, a sample 8 week plan for you would be 40-44-48-53-40-53-57-60, all easy, and should at no point feel debilitating. A key thing is to run as you feel, and rest more if you feel sluggish, as it is your body's way of telling you you're doing too much. I would not go higher than 65mpw this season if I were you, because as most great coaches will agree it is better to undertrain than to overtrain and put an athlete at the risk of burnout and injury. Also, don't neglect supplemental training such as core work and circuit training directly after your runs 2 or 3 times a week during the summer, as it helps your body stay strong enough to handle the increasing mileage. Once the season comes it is always wise to just do as your coach tells you because he knows you better than I do, and he will likely train you to your strengths and help you work on your weaknesses. This has worked for me and I am using this philosophy this summer as I want to run much better in XC and makes states as well as bring my mile PR down much lower as I ran 4:35 this season and want it below 4:20 the next. If you want to learn more simply google summer mileage cross country or similar terms on thoroughly read the articles that come up. It is always helpful to inform yourself by using a variety of sources and take the pieces from each that seem right for you. Good luck with your season and I hope you do well.