Purpose -This paper addresses the impact of Mean Time Between Disasters (MTBD) to inventory pre-positioning strategy of medical supplies prior to a sudden-onset disaster.Design/methodology/approach -We developed a trade-off model based on the operations of Médecins Sans Frontières (MSF) and implemented this in a spreadsheet-based platform to show the impact of MTBD on determining a pre-positioning strategy. This spreadsheet model identifies the most cost-efficient scenario out of a set of predefined pre-positioning scenarios. We implemented the model using a case study of a cholera outbreak in Zimbabwe.Findings -We are able to show the impact of MTBD on determining the pre-positioning strategy. In addition, we also capture the trade-off decisions in transport modes and end-of-shelflife policies. Moreover, from financial perspective, we show that an interaction between relief (emergency) and development (regular) programs can be beneficial.Research limitations/implications -We have some limitations on data access and availability. Some data (e.g. uncertainty in needs and lead-time) have to be collected for future research and, then, used to refine such decisions.Practical implications -The model can be used as a justification for selecting an inventory prepositioning strategy based on mean time between disasters (MTBD).Originality/value -We introduce relevant factors in a humanitarian organization's practice that have not yet received attention in literature (i.e. MTBD, inventory swap, and trade-off decisions in transport modes and end-of-shelf-life policies).