Hi Walter,
Goto WFA> Administration> WFA Configuration> Advanced
Change the value of option named" Maximum workflow job executions to keep"
BTW can you give us more context on why you want you to go back to a workflow execution log.
This option is based on lines to keep and not on age or days to keep.
If you could give the customer or case details.
Will add the same to the RFE already filed for the same.
Regards
Adai