Most people them the FD so the middle can be used with the middle and inner cassette sprockets, and don't plan on using the outer. But you can leave it that way if you expect to go to the granny rather than middle/inner combination. BTW- a bit of gentle rubbing once in a while in rarely used combinations is fine. Just don't have the cage rubbing in the gears you always ride. Before index many people would poorly trim the FD, and ride all day with it rubbing pretty hard.

I remember seeing them bring in repairs, with the FD cage worn all the way through, in some cases with a 5/16" section missing at the height of the chain on the ring. I always wondered how long it took, and how they couldn't hear it.