None of this damage happens dramatically. There’s no single bad day where a collection gets ruined, it’s just a slow fade that’s easy to miss until you compare a stamp to a fresh copy of the same one and wonder why yours looks tired.
Three culprits show up again and again. Direct sunlight fades ink and paper faster than most people expect, even light through a window counts, so keep albums and stock books out of direct light, not just out of a sunny room entirely. Humidity is the second, dampness encourages mold, foxing, and pages sticking together, so a dry closet beats a damp basement every time. And the third is the one we talk about the most: non-archival storage, cheap tape, ordinary paper envelopes, or old acidic album pages slowly damage anything they touch over years.
The fix for all three is boring and cheap compared to the damage it prevents: acid-free stock pages, proper mounts, and a dry, dark storage spot. None of it costs much. All of it adds up over decades.