In my experience, if you’ve hit 50 K and it’s not the end of the month – or the rough draft – yet, then keep writing.
Seriously, the momentum of having pushed this far on an idea cannot be underestimated. It’s much, much easier for me to add a few more thousand words now than it will be if I put it down for a bit and try to come back to it. It can actually be easier to keep up a high word count at this point because all of it is gravy; I have 50 K, I don’t have to drag out a few extra hundred a day if I don’t want to, I can relax a bit.
I’ll need to check my “list of things I still need to get into the story”, but I’ve finally gotten it to just a few days before Halloween. Now a bunch of stuff can get crammed in to a short period of time, as the bad guys try to crush the heroes physically and emotionally, and all the good guys fight back.
…And if I really need motivation – monster deer. Really. Mwah-ha-hah….