Joy,
Winter squash are typically not mature until the stem on the squash turns brown and is dry. Do your mature squash meet that criteria? If so I would pick them, but if not, I would leave them until they do. Certainly, I personally wouldn't pull the plant until it stopped producing squash. If any of the butternuts are produced too close to the cold winter and won't have time to mature, then you could eat them as a summer squash. Whether you'd prefer to plant something different than continue to produce squash, that is a personal decision. :)
Best of Luck!
Susan

Thanks, Susan. That answers my question. I'm just going to let these babies roll!