I have one at home that's 22 now. Not a huge difference from younger snakes, she has more mass to her - compared to 3 or 4 year old snakes, for example, she's a denser, thicker snake. Bigger head. Her hunger strikes are usually 4 to 6 months, and she's a fairly predictable old gal.
She's shyer than some of my other balls, much much more head shy, but she's always been like that. Otherwise, no real differences between her and my other big, mature females.
-Jen