After burning, or other disturbances such as logging, the forest responds with dense understory growth, increasing the 'fuel load' and flammability. Repeated prescribed burning keeps the forest stuck in this cycle of high fuel loads.
However, after a longer period without fire or disturbance, the forests self-thin due to the understory not receiving enough sunlight from the mature canopy. This results in significantly reduced flammability over longer time periods.
This has been confirmed by both data analysis and on-ground measurements of vegetation structure and fuel loads.
The DBCA often states years of large areas of wildfires are less common when 8% of the 2.5 million ha area under management has been burnt in the past 6 years (hence the 200,000 indicative target). However, analysis if DBCA's public records on fires shows that since 1950, it is actually MORE likely,noting that 'large areas of wildfires' are defined by DBCA as 1% of the area, or 25,000. The devastating Dwellingup fires of 1961 occurred after 6 years of more than 200,000 ha of the region being prescribed burnt.