My warranty, like me, is less than formal.
I am Skipper Custom Instruments, and my instruments are me. My name and reputation have been built over a lifetime, and are of utmost importance to me. I'll do whatever is necessary to both maintain respect for my name and for my instruments, and to keep you satisfied and happy as a customer.
A practically indestructible instrument could be built, I suppose, but I'm not sure anyone would want to play it. At the other end of the spectrum, one could construct one so vibrant and alive as to turn heads, but one so fragile that it would not endure for long. All instruments fall somewhere between those two extremes.
Skipper instruments are built with utmost sound as the primary consideration, while keeping in mind the demands of long-term, everyday use. They're intended for serious musicians who understand the nature of an instrument, and who provide adequate care and maintenance. Structural design is not of an experimental nature, but rather uses time-tested patterns that won't provide surprises a decade or two down the road.
Temperature, humidity, and strain are the factors that can destroy any instrument, or if properly controlled, can prolong its life almost indefinitely. Heat can turn your cherished instrument into a basket of loose parts, and cold can destroy finishes. Moisture will reshape your instrument in ways you neither expect nor appreciate, and dry air will supply you with a lifetime supply of toothpicks. In heating season or in dry climates, a humidifier made specifically for instruments is a necessity. Unless your instrument is specially designed for it, fence-wire-gauge strings will quickly destroy your top and neck. If you don't provide a proper environment for your instrument, or if you damage it by dropping it or by allowing your grandson to use it for a shovel at the beach, don't blame me. A drop of oil won't hurt your tuners at all, and an occasional rubdown with instrument polish will keep your instrument looking sharp.
Like your car, some parts of an instrument wear out. Frets don't last forever. Bridge pins wear out after many string changes. After many years, most guitars require that the neck be reset. Like the warranty on your car, items subject to normal wear and tear, aging, and mistreatment aren't covered.
All that said, here's the bottom line: if I did something wrong, bring it to me and I'll fix it to the best of my ability and at my expense. If you broke it or failed to control its environment, or if it's a part simply worn out through use or a problem that's a natural function of time and is common to most instruments, I'll fix it at yours, and as efficiently and expeditiously as I possibly can, and for as long as I can. Retirement is on the horizon, and there's nobody to pick up where I leave off. If you're reasonable and honest, you'll find me to be the same way.