A 2684 can take between 35 and 50 minutes per frame depending on your hardware.
and have folded at least 10 succesful regular (-advmethod) WU's before you can get the bonus for bigadv WU's
6061 is a regular A3 advmethods WU so thats perfect. It won't start to calculate the PPD until its done a few frames
Just wait till you've done 10 of them then you can switch the -advmethods flag off and the -bigadv one on.
What hardware are you running? Is it this?