ONBAR with ADSM

We are running informix 7.23 UC6 on IBM SP2 AIX4.1.5, ADSM 2.1.6. We currently have our level 0 and level 1 backups expiring by the number of version kept in ADSM. For logbackups, this is not possible because every log is unique, which creates unique files within ADSM. We have the class set up to expire these files after 12 days, but this is not working. After speaking to IBM, they say that the backup retention period only kicks in when the file no longer exists on the unix box. Log files never exist on a unix box in the first place except for within the raw devices. Does anyone know of a way around this, or have a different way of doing it? Thanks JP