I am now carrying more keys than the average Hig-School janitor, the question is will I ever need them again once they have been used? Is there some "Safe deposit Box" where one can store items you are tired of lugging around, but are loath to part with in some bizarre BGII garage sale?

Any ideas and suggestions welcome. They have scroll cases and gem bags how about a key-ring.

A key ring would be a fantastic idea. After all, keys are small and numerous.
unfortunately, there is no such item. Luckily, keys are never needed outside their quests. The key to De'arnise becomes useless as soon as Torgal falls. So you can chuck them. But I would still prefer a keyring.

If you are worried about losing a vital key, choose a barrel, chest or table somewhere convinient (waukeens promenade for example) and keep them there.

Or CC
Xen

The barrel just next to the entrance/exit to the Bridge District is IMHO the ultimate container. It's located only a few yards from where you start when going to the Bridge District, it's easily accessible and the map is one that will never change at any stage during the game, thus making it a perfectly safe container.

Four words for ya: "Jester's Bag of Holding" You'll find it in Spellhold.