Safety wire the bolts to each other or around the engine/muffler. Even if the bolts do loosen, there is nowhere for them to go. This will end your problems
Not necessarily. Depends on what is causing the problem. If the bolts are getting loose due to the muffler crushing at the bolt locations the wire will keep them from backing out completely but may not stop them from getting loose. The problem is not the bolts falling out. All it takes is a very slight amount of movement for them to get loose enough to cause the muffler to rattle. Once this starts, it can deteriorate the gasket (if there is one) and cause RF interference.