For as long as hmh has been held, it generally works this way.... in Sept. after labor day, The Haunted Mansion (Not the haunted house) is closed, then @2 weeks later, it reopens as the haunted mansion holiday. It remains open, until after Jan. 01, where then it will be closed down again, for another @ two weeks, then re open in it's more or less original state.
Refurbishments can and do take place at various times throughout the year. Keep eye on the refurbishment schedule on Disney's web site. It is a good idea to call as well, as your finalized plans begin to take place, just in case, you may need to change a date or two. That being calling Disney's guest services. Mind you, sometimes they do not have information available at the time. Hence, the importance of being mindful of the dates on their site. This forum is a good source as well as other Disney related sites.
Have a wonderful trip!