Your enemies in most forms of archival are humidity, light and UV, heat, and chemical processes. Some chemical processes are unavoidable, some others are caused by contact between items (a classic which is not well known is that PVC in some "protective" record sleeves reacts with vinyl records and eventually creates surface noise and destroys them) or intrinsic attributes of the item, for example acid in paper.

So preservation requires dealing with as many of these as possible. Archival box for starters which will be acid free and lightproof. Silica gel to remove moisture. Store in a temperature stable location. Use a buffer between items, for example acid free tissue or cartridge paper. You can't prevent everything, but you can work through issues. Bundling stuff together isn't always a good strategy for preservation but it does tend to sort out the light issue.