There was a thread about this a couple months ago. One member posted a link showing that most plugs come from the factory with treated metal making its use unnecessary.
I use it and will continue to do so. I use the guide on the box- As soon as the plug base contacts the surface of the head, I tighten the specified amount (forget if it is 90* or 180* further) as they are washered.
All that to say you will probably be told both ways.

Rich
Also, the manufacturer recommends a replacement interval. On the 1500 it is 8000 miles for my 2000. I usually double that, many go a lot longer.
It helps also if you include year and model as it can vary maybe? Maybe in your sig or under your avatar.