What I'm hearing from your body is simply that it is healthy, as it should be for a 26-year-old male. As my late 95-year-old grandfather-in-law said about life, but that applies to running also, "If you have your health, you have everything." Stay the course with your present training program, avoid injury, and live for more marathons next year.
Next spring, after gaining experience from your first marathon this fall, you will be in a far better position to modify your training program. You will know whether you will want to spend more time each week on speed or endurance, for example.
Many of the people responding on this BB are in their late 40's or early 50's (I'm 54). They will tell you, as North is doing, that running is a sport with at best modest weekly progress. The key is to ask yourself where you want to be in a few years as a marathoner, and to achieve that goal gradually and safely.
You can get confirmation of the need to stick to a safe training program by looking at the results for any previous marathon. You will see that the number of participants in each age group drops off dramatically with age. The decline is frequently due to bum knees and other over-use injuries.
Good luck with your current training plan.
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