Is she old?

My JRT, Polly has just turned 6 this year, i was wodnering if she is classed as old?
I know the averafe life span for a Parsons Russel is 14-16 years, but they are a whole different breed and i was wondering about a Miniature JRT, my aunts dog is 13 and still going strong, and i know of someone who had a JRT 21 years without vaccinations or being speyed, just a life of clean air and lots of working.
And my friends cats r 16, still going strong, well apart from 1, but that just shows u
So i would like to know if Polly is old, and how old do Miniature JRTs live
best wishes

i think you answered your own question if your dog is only 6 and some dogs live till 13 or 14