My manual says to be in 5th by either 40 or 45 MPH, I don't recall which of those two it is. Either is pretty ridiculous, I do remember that. Basically, they want you to go to the next gear at ~1500RPMs, if I remember right. Obviously this is impractical most of the time. I have done it in the past, when you up shift, you end up a bit above idle. It does not bog if you are accelerating like a granny with a back seat full of eggs. That is the best fuel economy, though.
The thing Is, I don't drive like that. I have at one time or another, like when my gas light has been staring me down for the last, well, forever. Other than that, the manual can go to hell on shift points. Closest I do to their recommendations is shifting at the "shift tone" drone of my flows, ~2100RPM.
BTW, I have a T45 in my 2000, so there are some different gear rations involved if your '01 is a TR3650 and not a T45 like mine (some '01s are, some are not - that is the year they made the transition). I think it is only first gear that is different in ratio, though. Maybe not.