Is 9 young for a staffordshire bull terrier?

No, not `young` and not `old`....but elderly. 

But in reality some dogs do age earlier than others.

All breeds of dog are considered aged when they reach 7 years old.

Most working dogs are retired between 7 and 8 years old according to what work they carry out. (yes, I know there  are exceptions). 

Most GSD`s die between the ages of 9 and 13 but one of my old working dogs lived to be 15 years old. He was still leaping over jumps at 11 years old. 

So like people, its in the genes (mainly) as to how long a dog lives. ( bar any fatal ailments). 

Keeping a dog lean and exercised and fed properly, will help prolong it`s life.

 Late middle age... They die between the age of 12 to 15 yrs. Danny my former staff  b itch lived til she was 13

Yes and Young enough to still cause a fatality. 

No. 9 is a senior dog. Their expected lifespan is around 12-14 years.