Based on what you said, and assuming you did a few 45 mile weeks in track, the jump to 50 mile weeks is perfectly reasonable. Many programs will run several weeks in the mid 60's by the time their athletes are seniors, and your program seems to be developing athletes along those lines.
All of this is said in very general terms. Only your coach knows his/her athletes and can make an appropriate training plan. It's not productive to make decisions for athletes that you don't see on a regular basis because you cannot see how they are adapting to the training. Trust your coach. On face value, it seems reasonable.
Buy a new pair of shoes, do all the supplemental things (stretching, strength training, drills, etc.), and communicate with your coach. You should have a good summer of training if you follow the big picture.