Everything is on topic, whether I choose to answer is up to me! On another forum, it is standard to start every well with the question: "One horse-sized duck or 50 duck-size horses?"
I'm not sure what you mean by the question on AA/KK because when we have AA/KK we are, by definition, at the top of our range. If you mean slowplaying, well, there are spots to slowplay for sure but not as many as most people think. I mean the limp-RR from UTG is cool when it works but how can you really balance that?
Someone once told me that you should be capable of having any hand in any spot. There is merit to that but like a lot of poker beliefs, you can only take it so far. Something AeJones once said was, "No one ever has anything." And this is very true; in two-card hold'em it is very difficult to make a good hand. Obviously, if you take this too literally, you will get into a lot of trouble.
Times to "slowplay" AA/KK: When facing a 3-bet OOP from someone with a polarized range. This is especially true if they might fold to a 4-bet because it just screams strength or you have a really nitty image and/or they tend to spazz out when you donk into them or cling to top pair/smaller overpairs like they're the stone-cold nuts.
Something a really great player (IowaSkinsFan) once said is that, "It doesn't matter if he bets it or we bet it."
Thing I've learned about poker concepts is that you can be scraping at the edges of a revelation or epiphany but just can't quite articulate it well enough to readily digest it. Once you find that person who explains it in a way that you can digest it easily, it will really sink home. Making a play in poker works much better when it comes instinctively -- of course, there are no real "instincts" in poker; you aren't born knowing that you should flat AA OOP. But when you accept something deep in your gut it becomes easier to make certain plays naturally without thinking about it too much -- this is especially important in live poker.
So if you have AA/KK and are facing a 3-bet, the pot is already pretty big. If you were in position and he raised, you'd be happy to 3-bet and get called. So who cares if he bet it or you bet it?
Sure, it's nice when you get the chance to 4-bet AA/KK, but if his range is polarized this is exactly what he wants you to do: To fold your weaker/middling hands (hands as good as TT/AQ or even JJ) and 4-bet the nuts so he can just fold his junk.
When people flat OOP to 3-bets they tend to have a very capped range of something like TT-JJ, maybe QQ sometimes AQ, very rarely AK. Regs especially will tend to put you on this range. This range is difficult enough to play OOP, it is even harder to play it when you have exactly what they think you have. The chance of an overcard flopping when you have QQ is 43%; with JJ it's 59%. If you cap your flatting range here your range is even further capped on Axx/Kxx/AKx boards.
Your range becomes a lot easier to play and becomes more profitable when you can have an overpair/top set on those boards, doesn't it?
Another spot to slowplay AA/KK: In an MTT when you are in EP facing a raise UTG with a lot of stacks behind you that are likely to squeeze.
This was long and rambling, hope that helps.