Have a look at this answer: Reduce Backup duration
If you make these changes you will be backing up the spool files (V5R4 and V6R1).
You could just change the Save Object command:
CHGCMDDFT CMD(SAVOBJ) NEWDFT(‘savact(*lib) SAVACTWAIT(0)’)
CHGCMDDFT CMD(SAVOBJ) NEWDFT(‘SPLFDTA(*ALL)’)
Or do them separately in a backup exit routine or CL backup job.
I don’t know what the limits are but I have yet to see an issue with them.