without getting all technical, there are a number of factors that control the lifespan of both melongaster and hydei. the easiest of which for the casual culturer to control is temperature. at 80* assuming the culture is mite free and otherwise healthy, the life span is approx 25 days. once they have begun to hatch. its unlikely your culture will remain healthy for that amount of time. life span can be increased by lowering temps, but the best way to continue to have ffs is by culturing them, relatively cheap and with a little practice and experimentation, relatively easy, although it may not seem that way on your first few attempts. jmo