The prevailing theory holds that D Layer absorption diminishes throughout the night, and that best reception may occur in the pre-dawn hours. All else being equal, and YMMV. Many USA NDB DXers begin their sessions around 1000 UTC during the season. This typically allows best chances for reception of weak DX to the West and NW.
Although the effect does not seem to be as pronounced as it is at higher frequencies, some grayline or sunrise enhancement DX also seems to occur at times. It is not unusual here in Chicago to see, for example, stations in TX pop up briefly around the morning terminator.
I see less sleep - or the purchase of an SDR - in your future if this addiction gets worse!