In Poor Richard's aphorism "A small leak will sink a great ship," what is the moral that is being taught?

Franklin's aphorisms were typically practical wisdom which the reader could apply to his own life based on his own experience and common sense. A "leak" in a person's own life might be interpreted as a small recurring expense that can add up to many hundreds or thousands of dollars over the years. An excellent example is cigarette smoking. Cigarettes are now selling for what seems to older people like myself the astronomical price of around five dollars a pack. Not a carton, but a pack! If a man started smoking only one pack a day at the age of twenty, he would be leaking $1825 a year out of his pocket, and if he continued smoking at the same rate for fifty years, assuming he managed to live that long, he would have leaked $91,250. But that would only be in capital. He would also have lost all the interest and compound interest he might have accumulated in that time. Furthermore, the price of cigarettes would probably continue to rise, and he would almost certainly increase his craving for nicotine over the years, so that he would be smoking two packs a day and maybe even three. In his lifetime this one "leak" could cost him as much as half a million dollars.

Most of us have "leaks" in our personal economies. As we get older and earn more money, we tend to develop more and bigger leaks. It makes good sense to look at our own lives, rather than worrying about Great Britain's or China's "leaks," and see what we could do to stop any small leak that is obvious. Americans are probably the most wasteful people in the world, so it should be easy for most of us to spot leaks. Examples that come to mind are unnecessary auto trips to the supermarket, leaving lights on in an unoccupied room, leaving the television set playing when nobody is watching it, putting too many postage stamps on a letter, using too much laundry detergent, wasting food, making unnecessary long-distance phone calls. In one of his essays (from which Franklin no doubt borrowed more than once) Sir Francis Bacon says to be especially cautious about incurring regular small expenses rather than worrying about big one-time expenditures. A one-time expenditure is not a leak, but a recurring small expenditure can definitely be described as a leak if it can be stopped.