A. On average, solar panels can last 25-30 years. It can go significantly longer than that, depending on the manufacturer, as the quality of materials used is important.
A solar panel's first 25-30 years is considered its "prime" condition. During this time, the panel can perform to the best of its ability. After year 30, assuming the panels are well-maintained and undamaged, they can still do their job but less efficiently. Depending on your financial situation, you can either keep using the panels despite the slow production of electricity or opt for a replacement panel that can convert sunlight to energy at a high rate.