Depends...
I think it probably depends on where you live and drive. I've had my 4R 1 year and just changed (at 12K miles). It was filthy! A handful of leaves and other debris, the filter media was a dark black in some places. So, I was suprised. Now, the dealer changing it is a complete rip-off. If you can use a screwdriver and have 5 min to spare, you can simply pop in a new filter. It's just like replacing your home A/C filter. Personally, I just used a Bosch Micron and think it is superior (from a thread on this forum -- search--). It cost about 23 dollars.
BTW, what does the stealer charge?