The length of the duration will cause more jobs to be stored in the database.
Snippet from the PBS Professional 2020.1 Administrator’s Guide, AG-521
13.19 Managing Amount of Memory for Job Scripts
By default, starting with version 13.1, PBS limits the size of any single job script to 100MB. You can set a different limit using the jobscript_max_size server attribute. The format for this attribute is size, and the units default to bytes. You can specify the units. For example:
Qmgr: set server jobscript_max_size = 10mb
Job script size affects server memory footprint. If a job submitter wants to use a really big script, they can put it in shared storage and call it from a short script, or they can run a small job script that stages in the big script, then calls it
As you can see here 1.8GB of data is space consumed by the jobs and their job description/request/environment variables/etc.