Thought I would add my opinion, It is true in the 3 years that I have had my 3D Printers I have also never run out of filament.

However have had the filament break during the printing of a model for what ever reason the filament broke. Initially this was the reason adding this simple run-out switch to determine if the filament had run-out or broke was added to my 3D Printers...

Though if you have a few rolls of almost empty filament you could print multicolored models to use up these filament rolls effectively.