First of all i have noticed that duplicates are not found when entering the same line multiple times with a different starting date.

Only when the date is an exact match will there be an alert. This should be changed to include all Lines that are still active on the entered starting date (Workdate when left empty).

Furthermore when finding these new duplicates, instead of just suggesting to delete them, there should be an option to close those lines on the day before the start date of the newly entered line. This to maintain older prices for purposes of creditnotes, returns etc ...

Also when a line is deleted causing no more prices to be active, the last active price should be reactivated (remove End Date).

Possible Pitfall would be temporary prices like promotional but in these cases an end date should be entered as well on creation of the line.