First, you need the storage space on the disks to do this.
Next, you need to justify that cost of retaining recovery data on-site.
If you can, then you can setup directories named appropriately for their function and that will provide logical organization of the data; you can also create a media set for the backup-to-directory device (singular in this case) with a two week overwrite protection period.
Also, LTO technology will allow you to backup data at the same rate or faster than the backup to disk. An HP Ultrium 460 (200/400) will accept data as quickly as a disk, and an Ultrium 960 (400/800) will accept it more quickly . . . hmmm.
I've replaced 20-tape libraries with one drive and have decreased the backup time significantly!
They are pretty cheap, too: http://h18006.www1.hp.com/storage/tapestorage.html
Stephen