I think that every time you log in, if you have only 3 days or less left on your subscription, it should warn you then, because some people have a delay in their payment. If you pay by BPay PayByCash, then it takes at least 2 days to process. Make the warning, 3 days left on your subscription, 2 days, and less than a day.

I hope this will help eradicate game time wasted by the payment process.

Outside of the US it can take up to a full business week,sometimes up to 9 days for payment processing. Even a 10 day warning would be useful. Perhaps a feature to toggle how long you want the notifications for?

Hmm, not a bad idea. Especially now that we're verifying email addresses and assuming we have some means of outside contact.

Or would you guys prefer a primarily in-game type of notice?

For me email notice is more preferable way. Maybe just set option in the site profile, where player may set days before end of the subscription, when notices arrive and switch off notices completely, if he dont want them?

Email notifications would probably be best, but an ingame message at somewhere between one and two weeks before the sub is set to run out would be good too.