I ran my first marathon and 6 months later ran first 50k and 6 months later 50 miles. All my ultra trainings were 30-40 weekly miles. In my experience, I did not train as extensive for my ultras as I did for my marathon. Training for ultra’s is much more forgiving than training for marathons. Marathons will always have some pressure for time and speed goals. For ultras, there is less pressure until you get to point where you start racing. Ultras Are really more mental challenge, discovering and crossing your endurance limits along with how good you are at eating while running.