How are your atties failing? Completely dead or just a lack of performance? If they seem to be completely dead, you might want to check the resistance with a multimeter by touching the center post and outside threads. Sometimes a center post will get pushed up enough to fail to make contact and the result will seem like a dead atty. If the flavor is decreasing, then you may want to experiment with adjusting the wick like dormouse says.
In either case, a week is very short for any atomizer unless you are really abusing it by getting it too hot, too dry, too wet, etc. I have never stayed with tanks for very long, but regular 510 LR atties typically last me over a month. Cartomizers only last for a week or so before the flavor drops off, but at $2 or less each, I'm willing to put up with that.