With proper mainteance generators can last for decades. Just like it's necessary to change your oil every 3 months with a vehicle a generator also needs bi-annual maintenance to prevent it from breaking down. The better and more thorough the maintenance, the longer your generator will function without the need for extensive replacement parts.

If you don't use your portable generator regularly it's still recommended you have it serviced at least once a year, but recommended 2x a year. It's also highly recommended not to store old gasoline fuel from one season to the next, unless it's being treated with a fuel stabilizer.