According to Official Guinness Records,
The longest marathon playing a trading card videogame lasted 38 hours and 22 minutes, achieved by Ilias-Dagis Argyriou (Greece), in Thessaloniki, Thessaloniki, Greece, between 2 and 4 of June 2017.Ilias-Dagis had been playing Hearthstone for a couple of years prior to his record attempt.Ilias-Dagis decided to break this record because gaming means to him fun, a reason to gather with your friends, share news, blow off steam or relax. The whole marathon was streamed via Twitch.Ilias-Dagis is also the current record holder for the longest videogame marathon playing Hearthstone.
For a complete list of 2017 records, please visit 2017 Guinness Records in Greece.