Sir Alex, manager of United since 1986, is still taking as much pleasure as ever working with top-class players, the current crop including the likes of Wayne Rooney and Robin van Persie, but maintains he wants to continue for as long as he possibly can.
He told the Daily Mail:"There have been so many wonderful players at the club and it has been a pleasure and an honour working with them.
"There's nothing I like better than to pull my car into the training ground of a morning and look forward to another few hours working with them and my staff.
"Any manager would be thankful to remember one great squad; I've had five or six."
The Scot has achieved unparalleled success at Old Trafford, winning 12 Premier League titles, five FA Cups, four League cups and two European cups, a haul that makes him the most successful manager in British football history.
Now approaching 71, Sir Alex enjoys legendary status among his peers, but his advice to fellow managers on their way up is simply to be themselves.
"I never tried to model myself on anyone," he explained. "I've never read any books written by managers. I have always tried to be my own man and do it my way.
"If I was to give any advice to young managers, it would be not just to learn by your mistakes but also heed the reasons why you made them.
"I don't just mean why your team may have lost a game, but all the other things that you have to attend to every day - your judgement of players, tactics, team selection, player welfare - everything."
Victory against newly-promoted Southampton would be his 599th win in the league, while 233 league games have been drawn and just 168 lost. His 999 games in charge have also seen 1,863 goals scored and 663 conceded.
Sunday's match at St Mary's will be approached with the same rigour and energy as his previous 999, with Sir Alex's main aim being to get the job done and get the win.
"I could never imagine how long I would be at the club or that I would be looking forward to my thousandth game.
"It may be a special occasion but it's just another game that I want to win."