I live in Florida, half-way down the Gulf coast. I know what you mean about food in the trunk. What I do is mix peanuts, raisins, and either candy corn or miniature jellybeans instead of the traditional chocolate.I put it in the peanuts jar and make a seal of that cling wrap you can press and seal to keep fresh,then put the lid back on tightly and dont bother to tape it.The peanuts still absorb some moisture from the raisins and taste a little bland but I treat it as a new taste and try not to compare it with freshly opened peanuts.When walking in the heat I have found that sugar is almost as important as salt. One of the components of treatment for heat stroke is an I.V. w/ sugar in it. I have had two bouts of heat exhaustion which left me chilled and shivering in 90+ degree weather; glucose tablets (those sold in the drug store in the diabetic supplies) were what stopped the shakes so I could function. I don't know of any food that will last indefinitely but this combination lasted two years in my trunk, and that was before I got smart enough to keep a cooler in there just to protect the food and liquid-filled compass.