Mass Submit and Approve Time Cards process is taking longer time to submit timecards

I am trying to submit 8000 timecards of saved and entered status using Mass Submit and Approve Time Cards process process with below parameters-

1. Number of threads as 3 and chunk size as 10.
2. Select only Submit check box
3. Select 14 days as in date range.
4. Select Group name for which we are running the process.
5. Select Saved and Entered status in values.

it takes around 4 hours to submit around 8000 of timecards.

Is there any way to improve the performance of Mass Submit and Approve Time Cards process so around 8000 number of timecards can be processed(submit) under 30 minutes.