The German midfielder has a contract at the Bernabeu until June 2023.
"Three years in football are long. Three years with Real Madrid are even longer," Kroos told Eurosport. "I definitely want to spend those three years at Real. Then it's a good time at 33 to ask yourself: what is the physical situation, what is the motivation, do I still feel like going on? And then we'll see."
Kroos -- who has been a key figure since joining Madrid from Bayern Munich in 2014, winning three Champions Leagues -- said he's reluctant to make another big move at this stage in his career.
"One thing you will definitely not read about me is 'Kroos goes to China for another two years' or stories like that. You can forget that," he said. "I can't imagine that it's an option for me to go somewhere else again. If something comes together and you say: 'Okay, another year here, because you're still good enough and you still want to', I wouldn't rule it out. But then another change, to England for example, where they play very physically, I can't imagine that at 33."
Kroos made headlines in April when he suggested he was opposed to pay cuts for footballers during the coronavirus pandemic, preferring to make charitable donations to good causes of his choice.
The Real Madrid squad subsequently agreed a wage reduction of between 10 and 20%, depending on how the 2019-20 season ends.
"I would repeat the same thing today. I have not apologised or had to apologise for anything," Kroos said. "The statement was made at a time when we were not even in discussions with Real about a salary cut. So, it was clear to me: As long as the club didn't come to us and say that they needed it to pay employees, it was unnecessary for me to waive my salary. I'd rather take the whole thing and use it to do something for those who need it more. But when the club approached us, it was clear to us that we would give up a portion to help."
One of Real Madrid's last games before COVID-19 forced football's suspension was their Champions League last-16 first leg with Manchester City -- a game in which coach Zinedine Zidane surprisingly left Kroos on the bench.
The 30-year-old was an unused substitute in a 2-1 defeat at the Bernabeu that Real Madrid will look to overturn in the second leg, if the competition resumes in August as planned.
"It was the first big game in almost six years that I wasn't in the starting XI. Of course, it annoys me," he admitted. "It would be bad if it didn't. It annoys me, but I had to accept it."