You can check the muffler bolts just before a flight... and still lose the muffler. Murphy designed muffler bolts.

Usually... the muffler starts comming loose and the engine tone changes... you get a warning and can set up for a landing. Occasionally the bolts BREAK... the muffler drops off, the engine dies and there you are suddenly short 2 to 3 oz of nose weight. Very few people can handle that. (I know 3 who can... I'm not one of them.)