I'm guessing you have to cancel or alter your plans for non-insurable reasons much more often than I do.

An I-fare to many parts of the world is well over £1500 even in sales. Of the dozens of non-flexible CW I-fares I've bought, I've yet to forfeit one; and if I did so the chances are it would be covered by travel insurance. Of course, some risks are not covered by insurance, but I can live with that to avoid the hassle of adding on four extra short-hauls (UK-Europe and back twice) to an otherwise simple return just to increase flexibility or shelling out thousands more for a C or J fare.

Yes, there are times when I need flexibility because my need to travel is somewhat beyond my control. But these are rare and then it's either a full miles redemption or travel on another airline.

Perhaps the real reason for all this justification is the fear than fully-flexible travel can get addictive - and very expensive. I have friends who always travel fully-flex, enjoying the ability to stay in New York another day because of an unexpected party invitation or show up at LHR for a later flight because they want an extra couple of hours in bed.