Ha! Good point, but, as usual, at least two sides to it. Often the main purpose of backing is simply to fill the reel--increasing the diameter of the arbor, essentially--so the line doesn't have the small coil and loads close to the pillars. The backing is just "filler," enabling the reel to be used for for different line weights and profiles. Nevertheless, "more than needed" as actual backing if a fish runs, is good policy unless you know you will never fish where a big fish can't be chased and can smoke across or down river, or back deep. Fish that move in and out of resting lies to go on feeding sprees like to "go home" when hooked. On big rivers or lake inlets, they can run out a fly line and 100 yards of backing in one or two runs. Even a drifted boat can't keep up, let alone an anchored craft, just for the time to pull anchor and try to follow.
The method of winding on the chosen fly line, then the backing to fill is still the best. You can then walk it out to wind up backing to arbor, or reverse using other reeels and then winding it backing-first to the reel to be used. It really takes no more time than looking up charts and guesstimating.
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