Molecular technologies have enabled the generation of various transgenic insect strains for the area-wide control of agricultural pests and vectors of human diseases. Individual maintenance of several diverse transgenic lines or strains involves a lot of resources, and sometimes problems arise that threaten the strains being maintained. Here, we present a way to cost-effectively maintain transgenic lines or strains of the Mediterranean fruit fly Ceratitis capitata by extending their generation time. Immature stages were kept at 20°C instead of 28°C, and the subsequent generation of transgenic flies kept at different temperatures were found to have laboratory fecundity comparable to the untreated transgenic flies. Extension of generation time offers inexpensive strain maintenance as it reduces the resources, time and energy spent on maintenance of transgenic medfly strains, in addition to minimizing exposure of strains to problems sometimes associated with strain maintenance.