ogletree - 1:36 pm on Feb 15, 2010 (gmt 0)
The answer is as fast as possible. You mention old posts. Page load time has not changed ever. Fast page load time is just important today as it was in 1997. People still get dial up speeds even on brodband. Anybody who has ever worked at a big company knows that there are times when the Internet is very slow. People at home might have other family members that are downloading movies or music.
Watch this video of Marissa Mayer. She goes into detail about how much load time improved bounce rate. Web pages should be under 100k.