What are teddy bear hamsters life expectancy?

I recently just dicovered my pet teddy bear hamster dead when i was going to give her food. Just about 10 minutes ago.... =( I would have had her for 2 years in january. When i bought her at the pet store, they did not tell me how old she was. Is it unusual for them to die that early? I did notice she got really fat (and I mean really fat) to the point where she would waddle. But people told me she was just storing away food cause it was winter, but she has not done that last winter. Could that be the case or was it just old age?