Originally Posted by JimBlake

As long as it idles OK, doesn't stall, & it comes up when you press the gas. If all of that's true, you want it to idle as low as possible. Much below 700 you'll find AC & the larger electrical loads will disturb the idle too much.

Sometimes people want to bump their idle up to 1000 or more just to avoid having to clean & adjust the idle control system properly.

Another reason might be a performance camshaft won't idle well at all under 1000 rpm.