24000, not bad, I had to replace my fronts at 18K
As you are only replacing the fronts I'd advise replacing them with the same tyres you are taking off to ensure all 4 tyres are the same. I normally move my tyres around so that I replace all 4 at the same time but never got around to it on the 500. I got my local tyre dealer to source a pair of the Continentals which were fitted as standard.
At the end of the day you need to choose a tyre based on your driving style, if you pottle around then you are probably more interetsed in tyre life. I drive my cars hard, even the 500 and I have to say the Continentals are just not grippy enough for me.
At the next change if I still have the car I'll fit Yokohamas which are much softer.