All seasoned woods tend to turn a dark color on the ends. If the areas where the insects have eaten are airy and spongy, then do away with them. We see no reason why you can’t use the good areas for barbecuing.
The only thing that concerns us about using wood that is very seasoned is that it tends to burst into flame quickly rather than burn slowly. The problem this creates can be a serious one if you’re not careful. When the old seasoned wood ignites, it can cause a fast rise in temperature in the smoker, causing it to overheat. Most folks want to quickly close down the air damper, which causes the fire to starve and create creosote. Creosote is a very unforgiving enemy of barbecue, for it only takes a minute or two for it blacken and foul the meat in the smoker. Once this happens, you can wipe and wash off the meat all day long, but it will never be the same. The oily, stinky smell will be on and in the meat. We didn’t read this from a book, we learned it the hard way many years ago. You must be very careful when using very seasoned wood, as well as green wood. So if you get a flare-up, open the firebox door to let out some of the heat, rather than shutting down the air inlet damper.
If you are going to use the wood for smoking only, and have another kind of heat source (charcoal, gas, electricity), then the cherry wood shouldn’t present a problem. Being as old as it is, soak it in water overnight, or for several hours before adding it to the heat source. It would probably be wise to wrap it in foil and punch a couple of very small (toothpick size) holes in it. You will be amazed at how much smoke will come out of these two little holes. Make too many holes in the foil, and the wood will stand a much greater chance of catching fire.