Just had something VERY strange happen - I went back to my IndieGala profile to see if there were any games / gifts I didn't redeem since I'm going to make a round of Steamgift giveaways.
Strangely - all of my "gift" purchases were reset! Some bundles, I purchased happy hour and sent them to my friends. Now I have the option of re-sending them to a new address! I tried it out by sending one to myself and I am assuming it generated new Steam keys.
So... I have a LOT of games to give away now.
First off, in reference to checking keys before giving them away on steamgifts, how can you tell which keys have been redeemed without actually trying them? Once you try them, if you don't have the game, the key gets used. If you do own the game, you just get a message that you already own the game. You get this message regardless of if the key has been used or not. In fact, you could use a key that you know for a fact is used, and if you already own the game, it still just says you already own this game. There's no indication of the status of the key.
Secondly, how do you know that you got new gifts? My assumption if I were in your place would be that a glitch caused Indie Gala to forget who I sent the bundles to. I wouldn't automatically think that I got new bundles.