Approaching his 71st birthday, and with over 26 years' service as United boss behind him, Ferguson's achievements at Old Trafford will be acknowledged on Friday with the unveiling of a statue of the Scot outside the stand that also bears his name.
Amid other little signs, including the health scare Ferguson suffered in May, it has been suggested it could be part of the end of his reign, and this season will be his last. But Charlton said: "When we made the decision to go for him we didn't in our wildest dreams think that it would last as long as this," said Charlton.
Charlton, who travelled back from Turkey with Ferguson after Tuesday night's defeat to Galatasaray, is putting no timescale on the departure, knowing just how difficult he is going to be to replace.
He added: "But from the beginning he obviously made people aware of what he did and how he did it with regard to controlling players and how to work with [the club] management which is also very, very important.
"I won't see his like again, I'm certain of that. We're really lucky, and people are really envious of us. He was born to do this job and he's going to be with us as long as he wants. He's just a sensational manager, I keep repeating it, [but] others must look on in envy."
As someone whose entire professional career has been played out under the guidance of one man, midfielder Paul Scholes is aware the time is drawing near when a change has to be made.
Some of the game's most famous names have been linked with the job. However, Scholes accepts, no matter who it is, they have enormous boots to fill.
"Somebody's going to have to come in one day and manage this team and if they do half as well as he does they'll be successful," said the former England man. There's nobody like him I know that - but somebody's got to give it a go. He has been brilliant for every single player that's worked for him.
"There is such a hunger and desire about him that really drives his players on - he knows how to keep you motivated throughout a season, it's something that he's managed to do for the last 20 years and I'm sure he'll carry on doing it for the next few years as well."