And as predicted, Wind announced last week that as of 28 September 2015 the credit will expire in 90 days with the sim card validity still at 12 months.

More info at the end of the announcement here (Google translate):
https://translate.google.com/transla...F%3Fprid%3D381

The Frog recharge number had a notice that as of June 26, expiry is now 90 days. Some time this week the web site was finally updated to 90 day expiry. I also notice that Cosmote Internet me karta also expires balances in 90 days.

Previously I would add extra credit to my Greek prepaid account just in case I needed them. I knew I could use the credit on the next trip. Now I will only put minimum amounts on the accounts and refill as little as possible as needed. More inconvenient, but not a problem for me.

Now that I don't have balances on my prepaid Greek phone account, I needed a way to get a refill card before arriving at the Athens airport.

https://www.telesuite.gr/eshop/ sold me a 10€ topup card for 10.88€ including commission. I also needed to get approved by their security before I could buy. After nothing happened I used an on-line chat from their website to get approved.

It is cheaper to buy codes from a kiosk, but I lost the slip I bought in Sept. My phone is now topped up and ready.