You know what the basic panel looks like...
Bottom line: the foam will disintegrate after about 15-20 years ... and into a gummy MESS. And it'll get into the air, irritating resp. tracks and making you/pets cough and sneeze. And you'll never get off clothes and carpets and books .... the stuff is like tar!
On this issue, I contacted the manuf ... several times ... and finally got a very brief response... where the rep. said something like ... the longevity I noted is about normal. (NOTE: nowhere on the SONEX manuf. web site or in its MSDS datasheet is there any mention of foam-cell longevity/disintegration).
I have several $K invested in Sonex, and that was mostly from 15-20 years ago ... and that "investment" is about to go dot.com, on me. I would NOT have invested in SONEX if I knew its lifespan ... and about the mess it creates!
Maybe they improved the formula since earlier manuf. runs ... let us know if your listening room or studio has crumbling panels.
(seems this problem is well know with long-time Sonex users):
Google "POLYURETHANE FOAM" for more info.