You're probably right. I do know that Season 2 of the Telltale game takes place primarily in a time between 18 months and 2 years after the outbreak, and there are still plenty of walkers and survivors. The reason I wanted to set it a good long time after the outbreak is because it presents a different sort of RP with different sorts of potential plot points, with hardened characters rather than complete rookies who don't understand how bites work.

I think I might reduce it to 18 months. That way it takes place alongside the game, but on the complete opposite side of the country so there's no chance of interaction. I wasn't planning to have any canon characters show up anyway, unless we happen to end up in a place that they could reasonably appear.