Just remember don't take any of this as LAW. Do what you think sounds good. Its your production and your sonic creation.
The reason for me doing what I do is I go for a very specific type of kick sound that isn't the most popular around these parts. My kicks are very Bass and Tick heavy, and when I say VERY I mean VERY. They are EXTREMELY scooped. Its basically just THUD and TICK. I like the bass of my kick to sit around 70 - 80hz, and the tick to be around 4k - 6k. Of course this is also for "metal" so I wouldn't be using settings like this for a punk band or anything poppy.
My bass guitars low end usually sits around 60hz, so I try and go about 75 - 80 with the lows of my kick, then scoop the fuck out of it!
The Panty kick in slate really ads a nice "smack" to the kick just where I like it.