kamalayka said:

Maybe the Millenium Falcom isn't as powerful a ship as the ones in the new movies. When Luke first saw it, he called it a piece of junk. Maybe Han's ship took a little longer to travel than some of the "higher end" models that were around.

Ah, yes, that would make sense. Especially since Han brags about how his ship is ridiculously fast and can out run Imperial Cruisers and make Kessel runs in impossible short times. Han is even surprised when Luke and Obi-Wan say they've never heard of the Millennium Falcon before. And doesn't Lando call it the fastest hunk of junk in the galaxy? Also in the EU always talks about it being superlatively fast.

It feels like the Falcon has always been built up to be this insanely fast ship. So I don't think the idea of it being older and slower stands too well. I am pretty sure this is a case of "let's do it this way" then later changing direction and doing it a different way.