Hope you're having a pleasant eavening all the way on the other side of the world, there tonight. (it's 6 AM here, IIRC that's like 9PM there, I used to regularly chat with folks from Australia and NZ)
You're going to find both answers on here. Some like to decorate their yard October 1, and have it up all month. TYPICALLY, these people are "display" type haunters, meaning they have a yard display for Halloween for people to walk or drive by and view. Then there are going to be those that only have things out a day or two early, or even only Halloween night. Reasons range from person to person, and include concerns about weather ruining props, theft, vandalism, and those of us who do a WALK THROUGH, meaning our guests walk through an interactive maze with actors and props. This typically takes a little more effort and organization, thus can't usually be done month long.
There are various combinations of display vs walkthrough as well.
Now, as for me, personally, my answer is yes.
I have some things that are actually up YEAR ROUND. Come October, I'll add little things here and there, and have been known to put up a scene or two that have absolutely nothing to do with what I'm doing for Halloween that year. We have the countdown sign at the center in October, and many people come by just to check on the sign.
That said, I take the week leading to Halloween off, and begin building 'for real'. The night before Halloween, we have an open house party. All the lights are on, and the neighbors come over and help us carve a crapload of pumpkins for the yard, eat, and enjoy everything with no scaring or actors. This is a great time for little kids to see everything. Now, Halloween NIGHT, the music is on and the actors are in costume and many kids, though they've seen everything the night before, are still awful scared Halloween night.
Now, in your case, I'd almost recommend attempting an indoor walkthrough so you can control lighting. A garage, carport, etc can be relatively easily converted. I've managed to make a reasonable show out of EMT conduit, fittings, and tarps to create an indoor space in the past as well.