Lots of variables. I have heard that the general rule of thumb, loosely agreed to by the industry is that they should last between 30k to 70k; obviously driving style is a huge factor so I wouldn't be shocked if people who do mostly highway driving, where you get away with 2 hours and no braking can make it to 100k.
Me. Pads were replaced with calipers at 60K, and I just replaced them at 110k. They had probably 10k or so more on them, but I was replacing the calipers and figured why not.
That gives them 50k of actual lifetime and in my estimate potential to be 60k.
If you are getting over 30k then I would imagine you got quality pads. Since how your drive and how you brake is so important to this, it is going to be hard to compare.