Not required. One media set (with proper OPP and AP) will suit your requirement perfectly.
Already pkh suggested the OPP value. (13 days)
Choose the Append Period as 1 Hour. (or None)
Start all B2D jobs as Overwrite only. Select the Media management setting as "Overwrite recyclable media in targetted media set before overwriting scratch media".
With these settings, BE will create/write to seperate bkf files, each time a job runs. So during the third iteration earlier backups will be overwritten. First week FULL backup set will be overwritten with third week FULL backup set, third monday's incremental backup will be overwritten with first monday's incremental.
Give a read here: https://www-secure.symantec.com/connect/blogs/faq-how-configure-media-setsb2d-jobs-and-backup-exec-proper-management-disk-space-while-using-
Regards....