I am a top pro triathlete and I ran between 40 -50 a week ran a 30:13 and Ran a Sub 2:30 marathon repeatedly. So I would say 3o might be a stretch but 40 is doable ... I was a collegiate All-American runner and I was amazed at how well I could run with less than half of my college mileage but with the amount of biking and swimming it really makes up for the non-running mileage and actually my legs were healthier with less impact injuries.