For degree holders:

Before 2015, it was common to spend about 2 years as GEO1A1 (3) before being promoted to GEO1A2 (4). This applied to both scholars and farmers. Sometimes they took 3-3.5 years, but rarely more than that.

After 2015, it was common for high tier scholars to take about 2-2.5 years, consistently good performing local scholars and award holders to take 3-4 years if their CEP was reviewed positively by their schools' panels, and others to take between 3 to 7 years.

The average is quite uninformative because there is such a wide spread.