Training question

So I want to get my fitness level to the point that I can run a marathon whenever I want as opposed to training for a specific race. Anyone have a rountine they use to do this?

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I personally don't use any specific training plan out there. I create my own based on my running abilities and personal schedule. Also If I want to PR or have a certain goal, that will factor in as well. I see what your saying because I run at least 3-4 marathons a year now and prob need maybe 12 wks to fully prepare if that but again depends on the goal as well. A PR or just running a marathon on vacation and wanna finish,etc... I know someone that runs a full every other weekend and uses them to train for the next one, etc...