Sophomore here, with similar PRs (16:27, 4:39, 10:18, @ 40mpw). While higher milage isn't a bad idea, I think right were you're at is perfect. It gives you some space to increase milage later on as you grow older, and seems manageable for someone of your ability. Now, if you were to ask me, does milage = faster times, yes, but only to a certain extent. Correct me if I'm wrong, but while there's huge difference between 30mpw-50mpw, there isn't much of a difference between 80mpw-100mpw. What am I trying to say? Increasing milage from where you're at isn't necessarily going to make you faster, although who knows, it might work for you. So to answer your question, I think that as long as you're running an amount of miles you're comfortable at, then there isn't a need to increase, or decrease milage. However, once summer comes in and it's time to build the base for xc, I don't see anything wrong with toying around with some higher milage.
-Leo