Actually a lot of other things can contribute to life shortening that are much more common. The biggest thing being overfeeding. Probably 90% of the snakes kept are overfed and underexercised. They don't need to move or hunt. They just sit and eat every week. Add to this newspaper which is slick and doesn't allow any real griping so they lose muscle tone as well. I'm not sure if its true but I have heard a few people say that boas kept on newspaper for years start to "pancake" as in they lose muscle tone and cant keep that square shape as they have spent years having to try and flatten themselves out to try and get grip on newspaper.
Not sure if its true but I use shredded aspen for all my snakes and as soon as my last 2 bails run out, i'm going to switch over to ReptiChips as a lot of boa and retic guys I've talked to have said the stuff is awesome and Jmcrook is using it now for his retic and says the stuff is great and not dusty.