Sheet protectors are not an archival panacea; they do not eliminate archival issues, add cost, and in some cases can increase problems.
The sad truth is that paper is pretty unstable and ultimately will degrade into dust. Paper conservation is about trying to fend off or delay the inevitable. As good stewards of the material we own, the obligation is to slow the breakdown of paper.
In my opinion the best conservation measure we can take is control the environment. Sheet protectors will not help with a poor environmental and in all probability increase degradation. In a good environment they help only by preventing mechanical damage (page turning, perfs 'fighting' with each other on facing page, etc.).
Is the money spent of sheet protectors worth reducing the risk of mechanical damage and increasing the potential risk of rapid degradation if the environmental conditions are poor? The answer from libraries, museums, and the archival community is 'no'. Keep in mind that we might not be around to ensure a good, stable environment, how we assemble our collections can easily outlive us and end up in a poor environment.
The second thing that collectors should be doing (beyond environmental control) is to occasionally test for acidification. It is cheap, easy and gives you an additional reason to look closer at your storage solution on a periodic basis.
Why is our hobby so slack about acidification testing? Do we just want to look the other way? Do philatelic suppliers not want to us to know that they are using the term 'acid free' when it is just marketing puffery? Why would we wait around until our stamps, covers, and paper reference materials are already showing signs of acidification (when it is too late to do much about it)? Buy a paper testing pen, replace it once a year (annual cost <$10), and test everything that is around your philatelic shelves. Album pages, album covers, album spacers, slipcases, boxes, 102 cards, glassines, hinges and mounts are all candidates for testing.
The added benefit is that testing schedule forces us into taking a closer look at our material every year (which is always a good thing)!
Paper testing penhttps://www.amazon.com/Lineco-Testi...p/B000KNJCSS