So, we first see Satele in 'Return' looking pretty young, this took place in 3,681 BBY.
The Sacking of Coruscant took place in 3,653 BBY, and from what I can tell, the game starts 10 years later in 3,643 BBY. That's 38 years. Even if she were 10 in 'Return', she's still pushin' 50 by the time of game, and she doesn't look 10 years old in 'Return', so let's say she's maybe 20 at that time.
I'd say she looks pretty spry for a 60-year old in game.
Ah, but as she is a Light Sided Jedi Master, would the force have preserved her to some extent?