It depends. The dwarf gouramies most commonly available are farm raised, often in poor conditions. They frequently have been exposed to a variety of diseases--internal parasites are very, very common in them. But, if you can find healthy stock, or are willing to spend the time treating them and getting them healthy, they are very hardy fish. Lifespan is around 5-7 years for most dwarves, longer for the blue spot color morph and some of the other larger ones.