Acid-free mattes

Earlier I asked membership a question on where they buy acid-free mats. I have just send back a summary of my research based on the tips given. While doing that research, however, I’ve learned that 1) There are “acid free” mats, which are made of chemically neutralized cellulose from trees 2) There are acid free mats which are made of cotton, which is acid free by nature. These can be twice or more expensive per unit. And there are a lot of folks with very strong opinions defending use of one, for the same purpose: Making the right investment to protect your artwork. Now the question(s): How meaningful is an obsession with “naturally acid-free 100% pure cotton rag” mats for protecting your artwork? How diminishing is its return? Or did anyone observe prints degrading noticeably within a decade or two in a “acid-free” mat made of cellulose?