I've never used 1st stage for anything except take-off.
What is a "stage" of flap extension? The Piper manual, like all other GA aircraft flight manuals I know of, describe flap extension in degrees, which is the way flap extension limitations are expressed on the Type Certificate Data Sheet.
Flaps are a form of flying control, the pilot can use them within the limitations of the aircraft, to control the flight of the aircraft to their preference. There is no limitation, other than speed, on the extension of flaps in take off range, at any time in flight. (Yes, I know about the "avoid" with slips in a 172, that's not a limitation). Doing so can be useful for many reasons, including formation flying with a different type, photography, maneuvering, and flying more slowly in reduced visibility.