I don't think 50k in one month of the year is a stretch, and I've even done it two or three times in a year, but spaced apart, and not every year. I can't do the crazy treadmill of full-time writing others do. I don't even want to.
I've only got 10k left on this year's NaNo and see no big issue with getting to 50k in the next three days now that I've recovered from my horrid cold. But then December will be revision time, not writing another new novel. I've got a novella to finish and I should in theory write another 50k novel in February or March to finish this series, really, I mean it, I'm done. But those are not my most productive months. Winter, ugh. For now, it's great to be as far along as I am on this story. We'll see what December brings.