The problems with WD40 are a few. First, its actually a kind of harsh cleaner, and can eat into small contacts. If you've already sanded them down, you'll risk holes in them. It'll also eat at the PCB, and make a mess.
There's two other problems though besides it's harshness. One is how it works. It has what amounts to a emulsifiers that allow the water to mix with the oil and run off, that's how it displaces water. Also means you can TRAP water in the oil for a while too, so make sure you dry it first if using it in enclosed areas. If the oil\water mix doesn't run off, you've made things worse.
Biggest issue though is when it dries the oils it leaves behind are gummy. They stay gummy for a long time; anyone who's used WD-40 in the winder to free a switch will tell you how they ruined a switch. In warm, dry air, it's not as bad, but you'll have a gummy dust magnet for a while.
Best way to protect them, dry packs inside cart boxes. Bitboxes would have less air flow than UGC, and will still have room for a drypack in the manual slot.