To maximize drive utilization, Symantec recommends that you do your duplication with as few Vault jobs as possible.

The more profiles you use, the less efficient the duplication process becomes. Drives are idle between the duplication steps of consecutive Vault jobs while Vault does all of its other processing (selecting images, backing up the catalog, and generating reports). It is much more efficient to use as few Vault profiles as possible for duplication. Therefore, if you can configure one Vault profile to duplicate all of your data, you reduce idle time and get the maximum utilization of your drives.

In Vault 5.0 and later, you can configure one Vault profile to create offsite copies with multiple, different retentions. By doing this, a single Vault profile can do all of your duplication, which keeps your drives spinning from the time of the first image to the last with no pause.