Meanwhile production Grids are robust and reliable Grid systems they are not able to progress as fast as Grid research would enable it and they do not grow as fast as they were originally expected. The remedy for the first problem could be the introduction of volunteer services that can extend production Grids with new services based on the latest Grid research results. Solution for the second problem could be the extension of production Grids with volunteer Grid sites deploying either the same or different Grid middleware used by the production Grid. Advance Grid portal service is a good example for the volunteer Grid services. Combining it with other volunteer services like legacy code service, brokering, monitoring it can even help in solving the second problem by enabling the adoption of volunteer Grid sites without compromising the robustness of the core production Grid, The acceptance of the volunteer service and site concept can contribute to the long term sustainability of production Grids.