I am extremely curious how asyncronous logging was multiplying the job execution by 4x - are you able to share a bit more information about what particular portions of the logging were costing time? If it was done asynchronously I assume you're collecting to-be-logged records in memory with occasional batch dumps to disk/other persistence but were you spending time collecting auxiliary information that was costing a lot of cycles? Like fetching relevant information from the DB that was useful only for logging and not for the actual job?

I've seen some time jumps with logging removal but I don't think I've ever seen anything exceed about 20% of execution time (at least on the scale you're talking about, there were some scripts I revised logging on that were constructing huge logging infrastructures for an otherwise sub-milisecond job) 40 hours is a lot of hours.