Vacuum duration + hint bits?

Hi, I have a question about a db-wide vacuum that I am running that is
taking a much longer time than normal. We switched over to our warm standby
server today -- which is virtually identical to the source db server -- and
I initiated a "vacuum analyze verbose". Normally this process wouldn't take
more than 6 hours, but so far we are well over 9 hours. I seem to recall
reading in one of these pg lists that a db-wide vacuum of a new (?) database
would go about setting the hint bits and cause a lot more disk IO than is
normal. Is that a possible cause.

Postgresql 8.2.13, RHEL5

Sorry, I realize I'm short on details, but I'm just running out the door and
the thought about hint bits struck me.

Cheers!