I spend my TCredits on Pricebenders Auctions and Eager Zebra games because doing this serves several purposes.
First, I get to enjoy the challenge of the auctions and the excitement of the games.
Second, I might win valuable auction items, and I might win rewards (or just 'Leader Board') in the games.
Third, when I spend TCredits, I also earn Member Rewards Points at TripleClicks, plus VersaPoints at SFI (up to certain maximum amounts of VP each month).
So, overall, participating in Pricebenders Auctions and Eager Zebra games ends up being a win-win-win situation for me. In my opinion, that is the most valuable way to spend my TCredits!
