Recommended interval for shift cable replacement?

[NHAero]

Came upon a friend by the side of the road recently with a broken rear shift cable, I think the shifter is an Ultegra 9 speed. Cable broke in the shifter. Is there a recommended interval, in time or miles, for cable replacement?

[peanutgallery]

Whenever you think about it. A good stainless/slick cable will set you back $3 and it's the worlds easiest install.

9 speed ultegra? Oi, that's like 20 years of service. Giving the Paceline's vaunted Campy a run for the money

[fa63]

I change mine once a year. Not that they really need changing at that point, but cables are cheap (and I do it myself so no shop labor to pay for).

[Matthew]

I honestly rarely ever change my cables. Never had one fray or break. I am a fair weather rider though and only ride in the rain if caught in it. If for some reason I swap out a group then I would but I believe they are changed more frequently than they need to be. Just my opinion.