The fantasy drama was renewed for a second season back in April, with new episodes expected to air in 2012.
"I hope it lasts for 20 years," HBO programming president Lombardo told Entertainment Weekly. "I promise you we won't stop it before it's ready to stop.
"There's a great relationship fans have with the show and we appreciate that. We've never seen people get so excited about casting [decisions]."
HBO co-president Pleper also insisted that the television adaptation will continue "as long as [author George R R Martin] keeps writing".
However, Lombardo confirmed that HBO does not have a "predetermined number of seasons" in mind for Game of Thrones, and also rejected the notion of expanding each season beyond ten episodes.
"If we could do 12 [episodes], we would," he insisted. "To produce those shows in the time they have, there's no way they could physically do more than ten... without diluting the quality."
Game of Thrones executive producer David Benioff recently revealed that a potential third season will begin to branch away from George R R Martin's original novels.
> Liam Cunningham joins Game of Thrones cast
Watch the Comic-Con trailer for Game of Thrones below: