My Warrior and Inquisitor are my two mains, and I imagine they were both around 22 at the Academy (they were there together). My Warrior was trained elsewhere up til that point, hidden in secret (for reasons to be revealed in my fanfic), and my Inquisitor escaped her slave master on Dromund Kaas at 21 and was found by a certain masked Dark Lord, who eventually brought her to Korriban himself.

3643 - Main Campaign starts (roughly) = 22 (as reference, Theron would be 23, Andronikos would be 35, Quinn would be 37)

3640 - Rise of the Hutt Cartel = 25 (Theron would be 26 and this is the same time he destroyed the Ascendant Spear, Andronikos would be 38, Quinn would be 40)

3638 - Forged Alliances = 27 (Theron would be 28, Andronikos would be 40, Quinn would be 42)

3637 - Shadow of Revan = 28 (Theron would be 29, Andronikos would be 41, Quinn would be 43)

3637 - Fallen Empire (pre-carbonite, I figure almost a full year after the start of SoR) = 29 (Theron would be 30, Andronikos would be 42, Quinn would be 44)

3632 - Fallen Empire (post carbonite) = 29 (still, and Theron would be 35, Andronikos would be 47, Quinn would be 49)

3630 - Iokath = 31 (Theron would be 37, Andronikos would be 49, Quinn would be 51)

I don't consider my characters as "aged" when they're locked in carbonite, whereas everybody else would have aged 5 years. Unless my assumption is incorrect and they do still age.

And yeah, so depending on your character's age, Nikki and Quinn could be some 20ish years older.