If everything is done by the handbook, that's one thing. But often things aren't. You should always have all of the fluids changed at the correct intervals, or it may lead to much bigger problems later..
And if you're unsure about the history of the car, just change it.. It's inexpensive compared to the potential costs involved with ruined parts..
Ie. $97 to flush power steering fluids. Over $600 to replace the rack etc..
If unsure, get it done.