We present a case study of the Las Conchas Fire (2011) to explore the role of previously burned areas (wildfires and prescribed fires) on suppression effectiveness and avoided exposure. Methodological innovations include characterisation of the joint dynamics of fire growth and suppression activities, development of a fire line effectiveness framework, and quantification of relative fire line efficiencies inside and outside of previously burned areas. We provide descriptive statistics of several fire line effectiveness metrics. Additionally, we leverage burn probability modelling to examine how burned areas could have affected fire spread potential and subsequent exposure of highly valued resources and assets to fire. Results indicate that previous large fires exhibited significant and variable impacts on suppression effectiveness and fire spread potential. Most notably the Cerro Grande Fire (2000) likely exerted a significant and positive influence on containment, and in the absence of that fire the community of Los Alamos and the Los Alamos National Laboratory could have been exposed to higher potential for loss. Although our scope of inference is limited results are consistent with other research, suggesting that fires can exert negative feedbacks that can reduce resistance to control and enhance the effectiveness of suppression activities on future fires.