One of todays greatest handbuilders said the best sounding guitar is one that's on the verge of flying apart. Over the years, I've found that to be the truth.
The body of an acoustic guitar is a bit of art, if done correctly. By design, the top, sides, and back have to be thin so they will vibrate, or resonate, well. The body would be much more stable if it was made of thick wood, but the tone would be poor.
The bracing has two primary purposes: stability and tone transfer. When you see a house being built, you see all that 2x4 framing before the plywood goes on. Pieces of plywood nailed together would never hold up without the frame work. The same is true of a guitar. Even if you use light gauge strings, you're looking at about 250 pounds of tension. The thin wood of the body would never stand the stress if it were not for the strength of the bracing. If the top bracing is placed correctly, tone will be transferred from the bridge to all points of the top, leaving no dead spots. To be good, an acoustic guitar needs to be fragile, or on the edge of instability.
Coffee tables last forever because their worst challenge is supporting feet, a family Bible, or a pizza box. Guitars are almost like an automobile. They need constant care and maintenance, or they'll break down. Just as your automobile won't cover cigarette burns on the seat, or engine failure because of a lack of maintenance; guitar makers won't warranty things that result from neglect or abuse.
Guitars are peculiar creatures. There's not too much that's bolted or screwed together on a guitar; most everything is glued together. You let a guitar get too hot, or too cold, it's going to come apart. You play your guitar outside when it's cold and then come back in the house with it, and it's going to attract moisture like a tea glass in the summer time. Since most guitars are unfinished on the inside, that wood is going to absorb moisture and swell. The moisture will make some glues let go; and when the moisture evaporates back out, the wood will shrink and often split and the finish will often get cracks in it. Remember, it has to be made of thin wood if it's going to resonate well. But the very thing that lends toward good tone, also lends toward instability.
There also needs to be a clarification between something that's defective and something that's worn out. Your automobile tires have a certain life expectancy. They may be expected to last for forty or fifty thousand miles, or whatever. But, no tire will last forever. The same applies to guitars. Strings wear out real often. Even the best of strings break down after they get salt and oil from our fingers on them. Frets wear out. Metal rubbing metal makes the strings and frets wear. I use very hard German silver frets, but they won't last forever. When the machine heads get old, the gears dry out, and often the buttons break loose.
Even if your guitar is free of defects, and you take good care of it, it's going to wear out eventually. Those old seat covers will crack, the radio will get crackly sounding, and it'll just wear out - kind of the way we do when we get old. I don't know of anybody who offers a full life-time warranty on a guitar. Most life-time warranties are called "limited life-time". I guess what that amounts to is this: the builder uses his judgement to determine if the guitar has been abused, neglected, if it's wearing out from use, or if it's defective.
I'm like most builders: I do a good job on building my instruments, and I want to stand behind my work. At the same time, I don't want to be misleading about what my warranty includes. Plastic binding and pickguards eventually pull loose. It's just the nature of plastic to shrink when it gets old. Truss rods break if they're improperly tightened. Finishes are continually wearing down as we rub our hands across our stringed instruments.
So here's my warranty. I use the best glues and finishes I can find. I hold, feel, and visually inspect every piece of wood I use. I told you most folks don't put a finish on the inside of their guitars, but I do. The finish on the inside preserves the glue from decay. If anything doesn't hold up on my guitars, I'm the final judge on the matter. However, you'll find me to be a very kind judge. I want you to be happy with whatever you buy from me. My name is the best part of me, and I want everyone to be able to think a kind thought when they hear my name. I want to do this job, and do it well until I go to see the Lord. If you buy an instrument from me, you'll get the instrument of your design, a case or gigbag, a photo album with pictures of your instrument as it was being built, and a two year warranty against defects. I've found that if something is defective, it'll show up pretty soon, and not years down the road.