If you can get them for fifty bucks, buy as many as you can like Polo said. That pack lists for $250. And you may see members here recommending other brands of dampener over DM but this is purely because you can now get similar performing products for cheaper. Nobody ever said flat-out that DM isn't good stuff, especially the extreme.
But don't buy multiple packs just because you feel like you can sell it later, unless you can do it local. With gas prices at record highs, shipping is very expensive and shipping heavy/low cost items like dampener kills your profit margin.
oh im not gonna sell it, im gonna use it all over my next car. i was just wondering if theres a life span in which i need to use it or if the glue goes bad or something idk. but ya im gonna buy 2 packs this weekend, some in my doors right now and then the rest for the next car.