I'm impressed you have been slacking and then still manage 12+ miles. I start to have ADD(attention deficit disorder) when I get around 5 or more and I workout alot. Long distance makes me nauseous just thinking about it. I get bored after 6 and see no reason to run any longer. Obviously I'll never be a long distance anything. Short, fast and sweet for me. Kudos to you for your stamina.