I don't think breakage applies, because I doubt they can keep the the lost/forgotten coins, just like unspent gift card money is not kept by the issuer.
Best Buy, for example, sets that level at about two years. In fiscal 2011, the electronics company recorded $53 million in income from gift-card “breakage,” or cards that are unlikely ever to be redeemed, up from $43 million a year earlier.
[1] http://www.digitaltrends.com/mobile/heads-or-tails-amazon-co...