Son, Father, Granfather backup strategy

Can anyone help me with a backup strategy i have heard about. It involves 3 sets of tapes:
4 * Mon – Thurs (Son)
8 * Fridays (Father)
1 * Monthly (Grandfather).
i wish to use it in a monthly rotation, retiring the grandfather each month, promoting a father and son and adding a new Son tape to the bottom of the pile.
(if your still with me) can you point me to a complete listing of how this rotation works and have you any opinion as to whether this is a good system.
Thanks in advance.