Solar panels generally don't require a lot of maintenance, but again, that depends on where you live, as well as how and where the panels are installed. Proper maintenance can influence both the effectiveness of the panels in addition to their longevity. For example, maintenance is required to ensure that your panels aren't shaded by trees (or overgrown limbs), leaf or other debris, dirt or dust. Even a small amount of shade has a large impact on the efficiency of solar panels. Panels operate most efficiently when they receive direct sunlight.
Areas affected by high winds in particular will require regular cleaning of solar panels. Dust from gravel, dirt roadways, fields, sand, and pollen all need to be removed. Smog in the city can also settle on your solar panels, blocking valuable sunrays from making energy for you. Wiping down panels on a regular basis will help to improve their effectiveness.
Winter brings a completely new set of issues with solar panels. Snow will block the panels' ability to generate energy, and the removal of snow is important if you want maximum energy efficiency. This can be dangerous especially if you have installed solar roof tiles and have a sloped roof, making them more difficult to clean.
A lifespan of 25 years for solar panels is reasonable. Regular maintenance (and repairs, if/as-needed) can help to extend the lifespan of the panels.