Depends how well you look after them - left out all winter, less than a year. Dried and stored properly every year, a good few years.

Hello there, begonia tubers in my own garden are lifted when they have stopped flowering and have started to die back , certainly before the frost . I keep mine in newspaper in the greenhouse and start them off again in the spring and I've had them for several years . Some don't come back again but it is worth saving them all in the autumn , and seeing what happens .