Just spent a month in Greece traveling around the mainland as well as Evia and Kythira, passing through customs in Singapore, Sydney, Istanbul, Athens and Manila with 3 batteries and zero issues. Customs had a few extra looks as it went through x-rays but absolutely no comments. Although I avoided flying it in Athens proper I managed to get some pretty cool shots over the monasteries in Meteora. The Greeks are generally laid back and nobody seemed particularly interested, let alone annoyed by my flying. Admittedly, I'm fairly conservative with my flights and tend not to go too close to other people.
Just though I'd share in case anyone is concerned about airport customs checks and lithium batteries, and Greece in particular.
Just though I'd share in case anyone is concerned about airport customs checks and lithium batteries, and Greece in particular.