your mileage is ok- its just how you do it!
Summer training should be relaxed to get mind and body refreshed from last season and ready for this fall and the races to come- hopefully wth improved times of course.
You weekly schedule might include a long run(15miles), 1 or 2 track reps sessions (12x200/8x400@rp 1 min rec) add some steady runs of 5-6 miles. Goal for summer is maintaining fitness and getting in some speedwork. Long run could include fartlek and or some hills.
Hope this helps you. But listen to your mind and body and rest if needed-watch for burnout! You should plan according to your goals/aims, lifestyle and level.
Good luck and train hard and smart.