I sometimes do, I sometimes don't. It all depends on how anal I'm feeling when I write something. Almost no one knows the difference between "then" and "than" and most of the population use them wrong. Language evolves...It's not like "its" and "it's" where people have no clue and the meanings are totally different. Or "your", "you'r" and "you're". Frankly, having all those different versions is stupid in the first place.
But I do know the difference between the two. "My friend and I argued that Chuck Norris is better than anti-lock brakes and then saw a movie".