Good topic / question. It's probably been discussed before, but if you can figure out how to use the search feature you're a better man than I am (duck!).
So if you're at all representative (actually the first response also), that could explain why folks sometimes ask for a 6th gear. Me, I never use 5th gear, let alone would use a 6th, and if I do use 5th it's for a few seconds till I downshift back to 4th to get a little responsiveness. (I think I used 5th much more on the way to and from NAFO.)
I cruise at about 5 or 6K and shift at about 6 to 7K. I keep it in responsive RPMs because I want to have power in a second if I need it. Of course, that could explain my lousy (34 MPG) fuel mileage.
If I need to get outta Dodge and then some, I'll take it to just before redline. I say just before to give myself a margin of performance because too many times I've hit the rev limiter, which of course defeats the purpose of quick acceleration, since it just goes "whiiiiiiiiiiiiig!"
JB