BE 2012 and capacity managed disk staging

In NetBackup there is an option to configure a capacity managed disk staging unit where NBU makes a "best effort" at keeping backups on disk, but if the space is needed for more recent or higher priority backups, it will expire the backups on disk to make room for the new data. Does Backup Exec 2012 have a similar concept?  The idea is that with 18TB of local disk and daily duplication to tape, I want to keep backup data on disk for as long as possible, but if I run out of space, expire the oldest disk-based backups to make room for the new (I already have a duplicate copy on tape so I'm still protected). I keep running into a situation where I have a fixed retention of 4 weeks for disk and 6 months for tape but I keep filling my disk after about 3 weeks. Instead of fiddling with the disk retention, just let BE manage it itself.