Hello David,
This setting is important for any lens that has this feature. Setting the focus limiter to the far setting will help speed up the AF aquisition and help prevent the lens from hunting if the target is low contrast. Its a must do! Give it a try. Once you do you can tell the AF speed difference with close and far settings.
When shooting with a macro lens with a limiter, its is important to set the limit to close to "lock out" far distances and infinity to prevent hunting and speed up AF. The best lenses will somtimes feature 3 limiters!
Robert