from a fellow BMW owner, our brakes are a blessing and a curse. for safety's sake, they are awesome. can stop on a dime. but they dust like a mofo. however, I must say that nothing looks better than having the wheels clean. add a little tire dressing and it completes the look. ask a female what they notice about a man's wardrobe...and 9 of 10 will say his shoes. same with a car...keep the shoes looking good, and you'll turn heads on the road!
I haven't applied a sealant on my wheels (yet), and I can feel your pain. but the 10 minutes I spend cleaning the wheels are 100% worthwhile for the 2-3 days that they sparkle. I try to clean them once a week, and that is only because of the curse of the beemer brake dust. there isn't much around it. it is absolutely amazing how dirty they get after only a few days. so hopefully I too will be able to update after sealing the wheels, but for now I'm content with a little AA cleaner (have about 1/4 bottle left) and mild agitation with a wheel brush. Every other wash I'll get in there with a wash cloth (a couple bucks for a dedicated wheel mitt is on my shopping list though) and get the inside as well.
the more you remove, the longer it will stay clean (obviously)...but our BMW wheels are definitely a magnet for dusting.