Supposedly, the new spec Motorcrafts are a lot less likely to stick - they have changed the heat range to minimise carbon deposits. I feel that if you use the new Motorcrafts, and install them exactly as specified - with nickel antiseize on the ground sleeve - you should be okay, and you need to use top tier gas too. Honestly, I have heard of a few people not getting good results with the Champions.
If you have to use crap gas, or don't get it on the highway frequently to blow it out, I'd probably use the Champions and change them frequently. This can get expensive - they are 15 bucks apiece.