What Media Creations said. The key to maintaining motivation for riding (or any exercise for that matter) is enjoyment. If you find that you can ride that sort of distance and still have the motivation to ride, I don't think it will be a problem. On the other hand, you might get tired of it, which means you might need to back it off a little.
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I am clinically insane. I am proud of it.
That is all.