I use the default scroll bars setting in OS X (Show scrollbars automatically based on mouse or trackpad movement), and I'm never not aware of the page length.

I see it whenever I switch tabs, and I see it whenever I start to scroll. I always have an idea of how long the page is and I don't need a constant reminder of it. It's not like it's a precision instrument anyway - who can precisely gauge the length of an article based on scroll bar length and current window size? Rain Man?

I can switch back to the always-on behavior if I want to, but I haven't wanted to.