The 70-year-old team founder and principal talks about the day when the lifelong love affair ends and the sport carries on without him but it is hard to accept that he will ever willingly let go.
Billionaire Ecclestone is still calling the shots and doing the deals at 81 while Williams, quadriplegic and in a wheelchair since a 1986 car crash, still has that gleam of excitement in his eyes that galvanised his team in the days of dominance.
"Many men marry and live with their wife for 40 or 50 years and shed tears when the wife dies," he told Reuters, sipping tea through a straw in a private office at the Monaco Grand Prix.
"These love affairs go on for a long time and I just love Formula One.
"I love my own wife as well, by the way, I've been with her for yonks, decades and decades. Sometimes she thinks for much too long but she's stuck with me," he grinned, with a wolfish sideways glance.
"I have got 51 percent (of the team) and eventually when I've decided I'm really in the way and I find it tedious and boring or I can't keep awake...," he allowed his thoughts to tail off.
"I don't foresee when. One day of course I'll come to it. Everything's got a finite end on this planet, including my mental health or love affair with Formula One. But there's quite a while yet I hope."
WHEEL OF FORTUNE
Williams, knighted by Britain's Queen Elizabeth for his services to sport in 1999, knows all about Formula One's constantly spinning wheel of fortune. From the early days when he borrowed and cajoled for funds, he has always been a fighter.
He has been through the heights of success, with Williams winning nine constructors' championships and seven drivers' titles from 1980 to 1997, and the lows of slipping steadily down the pecking order.
When Venezuelan Pastor Maldonado won in Spain this month, it was Williams's first victory in nearly eight years - their 114th of all time - and came after their worst season since the 1970s.
In Barcelona, Maldonado scored five times as many points in one afternoon as Williams managed in all of 2011.
'Maldo', as Williams calls him, was a 500-1 bet before that race but is now among the favourites for Sunday's glamour grand prix with Williams hoping to chalk up two wins in a row for the first time since Ralf Schumacher in 2003.
The timing could not have been better, with Monaco a key race for impressing and entertaining sponsors, but Williams shrugged that off in an unpredictable season where no team or driver has won more than once so far.
"It (the win) was not by superb management, I can assure you, but we take it whenever it comes," he said.
"We've only just begun our little journey here, if you like, to see if we can maintain this.
"When you've got a really superb design and engineering team you're there up the front nearly all of the time, you very rarely have an uncompetitive race.
"Yes, we've got ourselves up to the top of the precipice now, we're just hanging on there; getting our breath back. We'll have to wait and see. You'll have to come and talk to me again in six months."
Time was when Williams could turn up at Monaco with frustrated rivals breathing their fumes for most of the weekend.
In 1992, Britain's Nigel Mansell arrived with five wins in a row under his belt - but then lost famously to Brazilian Ayrton Senna in a McLaren despite starting on pole.
From experience, Williams knows that nothing lasts forever but that is also a source of hope at a time when others have quicker cars.
"The precipice is probably an unfortunate simile in many ways," he said, reflecting on his choice of words. "We are sound technically, financially, organisationally. We have a lot of experience, we'll be okay.
"But to maintain winning form...I can assure you that most team principals here, all of them with any sense, take nothing for granted.
"(Red Bull's) Christian Horner - how many races have there been so far this year (five) and how many have they won (one)? Are the good days over for them, will they ever come back again? That's what he'll be thinking."
The Spanish win was marred by fire sweeping through the Williams garage just as the team had gathered for a victory photograph and speeches.
The response, with teams from up and down the pitlane helping to extinguish the flames and then rallying around to offer equipment for Monaco, was a mark of the respect and affection Williams commands.
"I've had mail after mail offering us this and that," he smiled. "It has been unstinting and total. I'm very gratified but it would be the case for every team, I promise you."
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