How many miles you get out a set of pads completely depends on driving style, weight of van, type of van use, Camper or builders van, I know Steve fields and from talking to him he's still on the same pads for nearly 3 years.
I drive quite... What's the word... Heavy, sporty.
I don't dick about and get up to speed, I get all my braking done before a corner. I don't race I just don't hang about or hold traffic up. Get up to speed and get out the way was how I was taught. I haven't had any issues with pad wear.
Our Formentor on the other hand, stock pads, 7k miles (6k only me driving as Mrs Dav-Tec is still off the road) and the pads are 3/4 worn. Guess what will be going in shortly...