Our neighbors gave us about twenty male guppies about two years ago. Two of them are still alive. I just did a little research and it seems both should be dead by now. Guppies have a life span of a year or eighteen months. Two years seems to be on the high side.
Okay, how do I know they were all male you ask? I don't. I did threaten our neighbor that if he didn't give us all guppies that were either male or female, I'd bring all the babies back to his house. Given that he had so many fish because he had both males and females in his fish tank, he was careful to give us only males.
The fish just keep swimming along happily on the kitchen counter. Now that we have Oreo, they are completely ignored and rarely fed. They don't seem to mind. They just keep swimming along.