But in 2008 Hemphill decided he wanted out.
The result was seismic; new BBC sitcoms were cancelled, the expected Still Game series was stillborn, and the pair didn't speak - except for business or legal reasons - until a few months ago.
Today, they're laughing together in a comfy room of a swish Glasgow hotel, talking about their return to Still Game in the form of a new 21-night stage show at The Hydro.
Cynics will suggest the partnership is a marriage of convenience, with the minister being the agent who's pulled together the Hydro deal that will gross more than £10m.
"That's *****," says Ford, straight-faced. "We didn't come back for the money. We wanted to see if people still wanted us."
Greg agrees: "Everything's fine between us. And if people understood our friendship they would know that it never did get that bad".
For the next hour the pair reveal why this friendship was so strong they simply had to reconnect. And surprisingly, a packet of Walker's beef crisps, "wi' the corrugated ridges", played a symbolic role.
"Both of us hold receipts for payments from 1989 when we appeared in Blackfriars pub in Glasgow doing stand-up, and we got a tenner," recalls Ford of their first awareness of each other. "Bruce Morton, who was my best man, introduced us.
"Not long after, me and Greg turned up at Morty's flat at the same time to celebrate his fortieth. But as he opened the door, the chain was on, and he indicated he was 'indisposed'. So me and Greg decided to go to Cottiers bar for a pint.
"Greg offered me one of his crisps. But I'm no' disposed to taking somebody's crisps out of their poke - I'd never take food off someone's plate, but something in my mind let me take one of these beef corrugated crisps."
Hemphill wasn't aware of his new chum's minor OCD, but he did realise there was a connection.
"We got on like a house on fire," he recalls. "And we both loved Jewish humour, movies, American culture."
The pair came together when they became involved in the sex industry.
"I was running a call centre at the time which handled sex chat lines," Ford recalls, smiling. "Comedians and actors such as Bruce Morton, Stu Who? Jenny McCrindle and Greg all did stints."
In 1995, the pair heard of The Comedy Unit's plans to pull together a team of performers to write and perform a new sketch series, Pulp Video.
"We formed a real big friendship," says Ford. "And during the run we wrote some sketches together."
One of the sketches featured two old men (based on their uncles Sammy and Barney).
Pulp Video failed, but the shared experience, even the pain of disappointment, solidified the friendship.
Meanwhile, they were more skint than a clumsy schoolboy's knees. So, in 1997, they wrote a play. "We wrote it in ten days," says Ford, smiling.
"We called it The Bunker, because this little council flat seemed like a bunker," says Hemphill. "Then we asked Karen Koren, who runs the Gilded Balloon in Edinburgh, to put in on at the Festival, and she agreed, but said 'The title is ****, guys. Call it Still Game."
"LWT came to the Festival and bought the rights to it. They had the idea of starring Derek Jacobi and the Irish actor David Kelly as the old guys, with us writing it."
The network wouldn't take a chance on unknowns playing old guys. After three years, the rights expired.
"We got a couple of grand for the rights, and we were pleased someone had loved it," says Ford.
Meanwhile, when The Comedy Unit suggested Kiernan and Hemphill for a new radio show, the result was Chewin' The Fat, which led to four TV seasons of massive success - which bought the boys their chance at a sitcom pilot. But Still Game sat on a shelf for a year (budget restrictions) before being aired.
"Aye, but you could get it at the Barras," says Ford, laughing at the ingenuity of Glasgow's market stall entrepreneurs.
"Somebody had bootlegged it. And punters were watching the new TV show before it was even announced."
Still Game ran for six great seasons. But then the pals split when Hemphill, citing the pressures of business and deadlines, announced he did walking away. It was an ugly divorce.
"Trial separation!" says Ford, smiling, "Love is always lovelier second time around."
Greg joins in, grinning; "Burton and Taylor - that's us."
But if they could go back in time, what would they have done differently?
"Probably go slower," says Ford. "At the time we were looking at everything; new formats, new shows. And we were completely in a phone box."
Greg nods in agreement: "I felt if we'd done series seven of Still Game it wouldn't have been a great show. And the demands of TV would have caused us to burn out."
The years passed. The pair talked. The awkwardness dissolved.
"Yes, we had dialogue," says Ford. "Then we got to talking about the Hydro, and we agreed we wouldn't want to end our careers not having stood in front of a Hydro audience."
The death of Kiernan's 12-year-old boy, Sonny, later reinforced the belief that life is all too short for grudges.
But what of their future? The pair reveal they are in talks with the BBC about a new series of Still Game. They also want a deal with Australian TV, following the Mrs Brown's Boys lead. "And we'd love to take this new stage show and tour Australia with it," says Ford.
"We feel we can now be in control of what we were doing," says Hemphill.
"Plus, we really missed the characters. They were people. We wanted to see them again, to take up where they left off."
How was it sitting down together to write for the first time after their years apart?
"It was a bit odd," Greg admits. Ford cuts in, smiling; "Yes, but I brought a packet of Tunnocks' tea cakes and we got tore into them. That was us sorted."
l Still Game, The Hydro, from September 19. Tickets available.