I usually keep a set of drivers for each hardware. As an example, right now I have 185.85 and 182.04 for Nvidia (I many be wrong on the numbers but you get my drift). I do this so if I uninstall the driver and after I install the new ones, I encounter problems, I can easily go back to the previous one. When I get an updated one, the oldest goes to the bin... always keeping 2
Chipset drivers, for the most part, can be updated w/o a problem of corruption with the new ones... YMMV and this is only from personal experience.
Audio & Video drivers need to be uninstalled before installing the new one. Usually, Audio install will advice of this, video won't. Now, with Vista I usually like to uninstall, restart pc fresh, once at the desktop, I look for the newer driver I just downloaded, right click on the file and use "Run as Administrator", otherwise, I have experienced a lot of issues... Again, YMMV and this is only from personal experience.
I game a lot so I try to keep my Audio, Video and Display driver up to date, but up to a certain point, If it ain't broken... Don't fix it!