QUALITY ASSURANCE: Shinola is backing up its mission statement — “the belief that products should be built to last” — with a lifetime guarantee. Beginning Wednesday, the Detroit-based company will offer a lifetime warranty on all watches. “It’s really quite simple,” said chief executive officer Steve Bock. “We’re making a quality watch in Detroit. We started assembling watches here about 18 months ago and we really stand behind the quality. It’s one of the key attributes of everything that we do. If you are going to stand behind something, you might as well provide a lifetime warranty, and that’s what we’ve done.” Under the new warranty, any defects, excluding battery, leather strap and buckle, will be repaired or replaced with a new watch, free of charge. “It’s all about quality and buying a watch that’s going to be with you for the rest of your life,” said Bock. “The whole idea is to guarantee you the watch.”