This might work for some volunteers, but won't work for all. Volunteers who also have paid jobs may reject such formal systems because they are too similar to their paid employment.

People volunteer for a variety of altruistic and self-interested reasons. Some may be volunteering to enhance their own skills and career development. Also to motivate volunteers, you have to be motivated yourself.

What keeps you going? It's useful to revisit this question periodically, do you need to develop your role more? Do you need new challenges?

Praising volunteers is important, but it does have to be genuine rather than a matter of rote.

Giving volunteers targets and aims in their role specifications will help to make the recognition and review of their achievements an on-going process.

This is very true, also individual volunteer's motivations will change over time as a result of their volunteering and personal experiences. Be prepared for this and be ready to offer new opportunities and also accept that at times people may want to lessen their involvement.

If you are understanding and flexible with volunteers, you are more likely to keep their loyalty.