When BCWipe calculates 'estimated time', it just divides the disk free space size by some "average" write speed.
If wiping options are enabled, it adds some constant value. So the procedure may be not very accurate.
For modern fast disks (especially for SSD), the estimated time is larger than the actual time.
In right-click menu dialog, there is also the button 'Check' on the first tab - if you click the button, BCWipe will measure the real write speed and will give you more accurate result for this selected disk:
It is recommended to click this 'Check' button, and also to start the process and see the write speed and 'time remaining' reported on the progress dialog. You can always cancel the process if you wish.
If the drive has many files/folders, then 'wipe file slacks' and 'wipe directory slack' operations will take long time. It is recommended to configure 'Skipped list' to skip system directories.