Heat is another possibility.. like for example what they investigate on this video:
It could be that the weight of my truck (typically light... ) and the speed I drive (typically not super fast, though not poking along at a crawl either) or even the individual dirt roads we've driven just haven't brought mine over that threshold for generating more heat than they can dissipate while Grumpygirl's failed shock boots possibly a heavier truck, more hours of washboards, etc got the boots so hot that the rubber deteriorated. Both of us were in the same part of the country - I just moved away less than a year ago but I did a lot of driving out on the dirt roads near Kingman and Blythe.. so we were probably on similar terrain but the differences in truck weight and driving style could still produce a huge swing in heat.
This video shows the perfect example of what i preach when i talk about hi performance shocks vs conventional dampeners and why 2.5 body race shocks are soo much superior to conventional shocks in that type of terrain. Notice they were not even going that fast yet their trucks are having the dance of death with that fast/mini bouncing cycle while driving on something as simple as a flat fire road that if you keep it up for more than 10 minutes at 30-35mph you wouldn't be able to touch your shocks whithout having severe burns. My guess they kept going for longer maybe 10-20 min of that stuff and boom.... oil cavitates, shocks fade, seals go kaboom, shock shafts get destroyed and you need new shocks, assuming you can still drive the thing home from the trail..... Street shocks are not meant to whistand that type of abuse for very long so you have to lower the speed to get to your destination. 2.0 rear shocks might last longer, but on a heavy truck like ours, much longer depends on your abilities to recognize the shocks might not keep up with your right foot
same for the 5160's, the res can help keep oil temps in check, but their internals are not near 2.0 race ones and they can't be rebuilt. 2.0 race shocks are serviceable, 5160's are throw away and get a new pair.
That is one of the reasons i point to people when they want to have much more fun than that while offroading, and a pair of King, Fox, Radflo or Icons 2.5 all around can not only do that for hours, but at triple the speed if you have the cojones.. is another world, trust me their voices wouldn't even break up like they did on the video, You can sip a cup of cofee at 50mph the truck will feel like you're riding on pillows gliding around the terrain with the good chit.. More expensive sure but you get what you pay for and in this case believe me is that noticeable.