Someone had told me that demand for travel trailers\5th wheels is highest in the spring, and demand for motorhomes is highest in the fall.
With that said, we bought our motorhome in June when we were ready, and we were able to take advantage of a model year update. We purchased a 2014 on the lot for what I felt was a good price compared to the 2015's the dealer had on order and wanted to make room for.
In Central IL where I am you might have more luck dealing in the dead of winter when not much inventory is moving, but I'd also be willing to guess you could get that same price in July if you are a firm negotiator.
Not sure if that really helped much.
Best of luck to you in your search!