Fundamentals review

Ok...I definitely agree with raising the AJ. I just wanted to get some discussion going on this thought process, because I have also talked with players who limp in early position with big aces and KQ type hands. Does any one else ever do this? I used to raise every time, but at times I have limped just to mix it up and add deception. I have won some big pots using this method but also end up throwing away AK more than I like to. I think playing this way lowers variance but I don't think it is the most profitable way to play. Any thoughts?