Best thing is you are vested after 10 years of service and after 10 years of service you no longer pay into the plan.
It's very generous. If you are of retirement age, you can live on it with Social Security. It pays 2% of your final 3 years salary averaged multiplied by the number of years worked.
It's really the only retirement option available. It seems fine, but it would be nice to have more options.