The mufflers are literally triple wrapped, so they can often have holes in them for years and years before they finally let go. Mine had the outer layer ripped half off for years and were silent.
They finally failed by breaking the welded on connection of the front of the muffler. The mufflers had metal hanging from them that hung 3-4 inches off of them, but they didn't leak any sound or exhaust.
I wouldn't touch them unless you just want piece of mind.