Why wouldn't 3 days be enough? The default Target CPU run time is 8 hours.

.. do you have BOINC set to suspend work while the computer is in use?

Is there a particular programme that is impacted by crunching? If so, you can set BOINC to stop crunching when that programm is in use, but keep working the rest of the time.
My system uses all cores & threads all the time with no impact on other programmes or system responsiveness.

Just like Seti, and all other projects, it takes time for the Manager to get the Estimated processing time to match the actual time. With the longer running Tasks, it does take longer for them to adjust. And it's best to run with a small cache to avoid getting more work than you can handle when applications change or you get dodgy Tasks.

Computing
   Usage limits	
        Use at most 75% of the CPUs
        Use at most 80% of CPU time -> to keep 'snappyness'

   When to suspend	
        Suspend when computer is on battery (selected)
        Suspend when computer is in use (not selected)
        Suspend GPU computing when computer is in use (not selected)
        'In use' means mouse/keyboard input in last 1 minutes
        Suspend when no mouse/keyboard input in last --- minutes
        Suspend when non-BOINC CPU usage is above 60 %
        Compute only between ---

   Other	
        Store at least 1 days of work
        Store up to an additional 1 days of work
        Switch between tasks every 60 minutes
        Request tasks to checkpoint at most every 30 seconds

   Disk
        Use no more than 5 GB
        Leave at least 50 GB free
        Use no more than 10 % of total

   Memory
        When computer is in use, use at most 50 %
        When computer is not in use, use at most 90 %
        Leave non-GPU tasks in memory while suspended (selected)
        Page/swap file: use at most 50 %

Seti@Home:
Final data is in the splitter queue.
As promised, we've stopped the process that puts new data into the queue