rspo/req_lifetime is a SAP Parameter attribute which is used to control Not used information. This is available within R/3 SAP systems depending on the version and release level.
Below is the standard documentation available and a few details of the attributes values .
This parameter defines the default value for the retention period of a
spool request.
Value Range
1 to 8 days.
Caution
Value 9 means that the spool request will not be deleted. This should
not be set as the default value.
See SAP Parameter Documentation for full SAP documentation for this profile parameter.