I think giving him another month only enforces his stance that these dates are guidelines. It is fine to say it only once, but you need be more definitive then "I'll give you some more time."
If you've already told him that he has till end of November, then I think you are stuck with that timeline. If you haven't, then I think you need to give him a specific date he needs to be out. And honestly, I think another month is too long, especially since he has mentioned a December vacation. I can easily see end of November coming and him saying "well, I won't be here in December so can I just leave my stuff here until I get back." type scenarion.