The most resistant pattern is one shaped like a tire tread. It has maximum edge and causes variable rates of spread which disrupt a flaming front out of control. But all fires are dependent upon fuel loading and density, wind, and moisture. So one variable can change how big of a buffer you need. Basically, the amount of biomass that needs to be removed is a function of how fast it accumulates, as it would be extraordinarily expensive to keep up, so we don't. Ecotypes that had a history of burning every few years cannot be forced into another regime easily. Building a house in a place that wants to burn ecologically means eventually you will be visited by fire.