You're probably fine. I think once most people are at a mileage that is sustainable for them, they can just stay there for a long time if they want to. And there is something beautifully simplistic about that. So much of running is chasing more. More miles. Faster times. Just run the amount you like to run. I dig that.
But, be open to dropping down every once in a while when you need it. Life gets busy, calf gets tight, you over reach on a workout, whatever, just ease up a little bit.
Although for me personally, I'm more likely to cut workouts before I cut mileage. I just feel best when I do it that way.