Well I'm only 62 myself but I'm still not interested in a long walk due to a depleted or damaged battery. What I decided to do to be prepared, is carry one of the light lithium battery boosters available these days for probably less than the cost alone of another battery.
With this thing if I need I can boost the battery, I don't have the weight penalty of a whole nother service battery, I can boost someone else with it if necessary (or charge a handheld device), and I don't have to install and wire anything.

That appeals to my lazy side.