What about a credit system (like with credit cards). The player gains positive credit on their account when purchasing games and accumulating game time without asking for refunds. Time for good behavior.

The default cutoff for a refund will be still be 2 hours but those with "good credit" could possible have their cutoff set at 10 hours. Requesting a refund subtracts from your credit but it won't be daming as long as you're not someone who refunds every game that they purchase.