These depends on what kind of a mouse and what kind of environment you’re talking about. To keep it simple, we’ll stick to the simple house mouse. The house mouse can leave in the wild for less than a year. That’s okay, because the mouse can easily give birth any time of the year.
A female house mouse ovulates often and with little time between. When the house mouse is in a controlled environment - a research lab, a house, simply somewhere that they cannot be hunted - they can live for two to three years. The house mouse is one of the least endangered species in the world. They breed so virulently and quickly that there is little chance of actually endangering them for a while.
