For me, weather has a lot do with it. Living in here in Southern California, just last weekend it was 90 degrees out. And for as much as I wanted to, I just couldn't get into the Halloween spirit as much as I would have liked to when it's that hot out. At this point it really hasn't cooled down at all from Summer time. Even during Christmas time it's been hard to get into it because it often is warm here in December. So this year, it wasn't until last Friday that I finally dug everything out and started putting it out. I'll finish with the lights later today or tomorrow.
Whereas I know if the weather was much cooler and more Fall-like I can get into it much easier. So much so that even by mid-September I can already be in full Halloween mode. I actually plan to move somewhere with a much cooler environment, and a big reason for that is my love for the Holidays and wanting to revel in it as much as I can.