The norms of what administrations do changes over time in part because what administrations need to do change over time. It's obviously not helpful to contrast George Washington's executive behavior with George Bush's.

In particular, it's useful to draw a line pre- and post-USSR, as that was a sea change in executive policy. That means Bush 1 / Clinton onward. Other common markers are pre/post Great Society, pre/post WW2, pre/post New Deal, etc.