"I'm an old man but I continue," he said at a news conference ahead of Saturday's game at home to Crystal Palace.
"I feel good. For me my job is my life, I want to carry on.
"When I started at 35 I said, 'okay at 50 I finish'. When I arrive at 50 I said, 'why now, 55?' Five by five, step by step, 65, 70."
Returning to English football in 2015, 11 years after being sacked by Chelsea, appeared to give the likeable Italian a new lease of life.
After turning Leicester into English champions for the first time in their history, his task now is to improve the form that has brought such a stuttering title defence.
Languishing in 13th place with two wins and eight goals from eight games, City have scored only one goal in their last three league matches and lost 3-0 at Chelsea last time out.
In the Champions League, however, they are well on the way to qualifying for the knockout stage after winning a third successive tie in midweek, against FC Copenhagen.
"We made a very good match on Tuesday, but now we think of Crystal Palace," Ranieri said.
"They are strong and tall, similar to Copenhagen.
"Palace are strong at the back and then they have good players at the front. A good team and well organised. We must be clever."
Captain Wes Morgan, England striker Jamie Vardy and Welsh midfielder Andy King did not train on Thursday but are all expected to be fit for Saturday.
(Reporting by Steve Tongue, editing by Pritha Sarkar)
