I've personally never heard of an "ideal range" for rudder travel. I'd tend to not want to further limit what the manufacturer put in place - even if I only used the extreme ranges occasionally or not at all. Like Justin_NSA was inferring, there may be times when you need the additional deflection (e.g. docking) and it would suck to not have it at your disposal. Kind of like asking "what's the ideal fuel range", and then replacing your tank with "excess" capacity to hold only that amount of fuel. What does it hurt having the extra capability, even if you only rarely or almost never need it for any given trip? Even your idea of using extreme rudder deflection as a brake is a valid reason to retain the capability - what if you had to dock or grab a mooring without power, would that come in handy in that rare circumstance if you misjudged your deceleration and needed extra help to slow down?
As a guy who works with data for a living, if you really wanted to answer this question you should gather data on YOUR needs, and use that as your answer. So start taking notes on how much rudder angle you input, and for what purpose, and under what conditions. Then when you have data for all purposes and conditions, you'll be able to see the range that you use, and make a data driven decision to change how your boat is set up.
In the end you get to choose how much rudder angle you use for steering the boat under varying circumstances, so you don't ever HAVE to use 120 degrees if conditions never call for it. But what if they did...would you have wanted to give up the option to use it by blocking it?
