The 33-year-old, who has been with Real since childhood, saw sporadic game-time last season, but has re-established himself as the club's first-choice goalkeeper despite the summer arrival of Keylor Navas from Levante.
"Madrid's so big it seems like winning the European Cup only buys you a month," Casillas told The Guardian. "When you come to this club you need a crash-course in impatience. There’s no time here.
"There’s always speculation but after all the stories, the rumours, I’m still here.
"There’s never been a chance for me to go anywhere else because I’ve never thought about it.
"All the presidents I’ve had have said: ‘The day you don’t want to be here, just come and tell me.’ And I’m still here. It started here and I want it to finish here.
"I think I can play until I’m 40. I feel fit and strong. If your head and body are fine, you can do it. And if you’re happy, if you have got a target, you never have a reason to go anywhere else."
Meanwhile, the decorated Spaniard sees no reason why Madrid can not claim Champions League honours again this campaign as they prepare to host Liverpool tonight at the Santiago Bernabeu.
"We waited a decade for La Decima," he pointed out. "Now we’re thinking about the 11th European Cup.
"And we’ve got the team for that, so why not?"