I had better tell dad then, because after 20 years and 150k (truck has 280k) the valves on his F-350 may die at any moment...
BTW, Magnaflows are built basically the same way as a glasspack. They last longer and cost a lot more. I had a true dual glasspack catback system put on my F-150 and the $30 Thrushes outlasted the pipe the shop used. Glasspacks are still red but the paint is flaking around where they welded them to the pipe. So really unless you go full stainless I don't see the longitivity of the muffler being a huge concern.
Sounded freaking sweat before the pipe went all swiss cheese on me, much like a stock Mustang at idle and very much like of Eleanore on the Gone in 60 Seconds remake when I got on it.
Heck, the OEM mufflers for my tractors are basically a louvered glasspack without the glass (a small pipe with louvers running thru a bigger pipe) that is attached directly to the manifold. I go plowing (very high engine load) all day long and valves don't burn.
Magazines are a terrible resource for such things, they will bash anything to sell whatever product their sponsers want them to. I take them with a grain of salt. IMO it was a scapegoat for not adjusting valves before hydraulic lifters came out, or an improperly tuned carb, or misadjusted timing.
Glasspacks have been out for what 50-60 years? If they were so bad they would have died out decades ago... and there would be more on the net besides people that have no experiance with them so positive that they burn valves spreading the rumor... and virtually nobody out there having problems with them.
I did have one on my 2.8 for a little while... did not like the sound at all.