You do not need to change your oil so often, things are not the same as back in the 80's...
Sure the first several should be done in rather short periods, but after that, filters have gotten to be much better, and teh oil is more resiliant..
If you do a lot of driving, or hard driving, then you may want to do it at like every 3000 miles/ 5000 km.
I know that I am going to change the oil once I get to 2,000 km and then again @ 5000, from their, probably every 8000 km, I am also gonna switch to synthetic on my first oil change..
Why is it transmission fluid is only changed every 25,000 km, but engine more often. There is just as much motion in your tranny, and is more intricet than you engine.
The only reason oil changes colour is because of the detergents in it to help clean.