Only if you want to manually toggle sites on and off. If you use GPS and Location Control, the scanner will automatically toggle sites on and off as you move around.
If you are monitoring from from a fixed location only, you can "avoid" all sites that are not within your listening distance and the radio will scan the remaining site(s) more quickly. Same goes for talkgroups that you don't or can't listen to. With everything on, it will take almost 30 seconds to scan the entire Stars system each pass.