30-40mpw is good. Towards the middle of the season it might be okay if you end up a bit closer to 45 but it's really an individual thing. Definitely don't let your mileage get too high early in the season because it'll make you way more likely to burn out. The quality of your mileage matters more than the quantity anyway.
In my experience 50mpw was probably excessive during the season and works better for building a base over the summer, but again it's really a matter of individual preference. Just don't increase your mileage too fast, and if you start getting really tired/sore all the time it's a sign that your mileage is probably higher than it should be.