"I'm getting beyond the future now. I still have a lot of passion. I'm still happy," he told the Daily Mirror.
"But I'm 66 now - maybe three years more, then I'll finish
"The thing about football is we have some potential young managers but, because of the dangers, the hazards of management, they may not be there in three years' time," he said.
"The change in football is so much so quickly. If you're not successful in three games you could be away. All these young managers we've seen over the years are not there now."