I play mainly and only with wolf packs, only in 1942, this one appeared after about 12 hours of chase.
In this case, they sank one trader, damaged several, but it is possible that there were other sunken targets, because there was only one destroyer in my area.
Usually, if the option is selected from the selector "less reports" appears faster, i had a case in within 2-3 hours.
Alex is right, the attacks take place mostly at night, but I've had a case during the day
