Retailer John Goldsmith says Sunday trading has saved him from the onslaught of competition from online retailers.
Mr Goldsmith, who owns Kosmic Sound and Lighting, is one of many owners taking advantage of the relaxation of weekend trading two years ago to open his Osborne Park and Cannington stores.
He believes it is the single factor that has helped his business through tough economic times.
"When bricks and mortar shops open on Sundays, they give people who might be tempted to shop online on Sundays a place where they can go and buy things," he said. "It has been an enormous advantage to combat the rise of online shopping."
Mr Goldsmith said he was first sceptical about the benefits and took more than a year to take advantage of the changed laws.
Part of his concern was how it would affect staff and whether it would boost sales.
His concerns about sales eased immediately when he tapped into a new pool of Sunday clientele, including clubs, bands, churches and other groups who wanted to shop as a group. But his staff first railed against the change.
"Music is a very chilled out industry and I knew there would be some pushback against Sunday shifts," he said.
"But in retrospect, they made it fit their lives and they appreciate the penalty rates they get for working on Sundays.
"I think everyone is pretty happy now."
But another retailer said her Sunday trading experience was vastly different.
The northern suburbs clothing retailer, who asked not to be named, said she stopped Sunday trading because it did not add to sales.
She had also been forced to work on Sundays because it was uneconomical to pay her staff the penalty rates.
Her seven-day work weeks left her exhausted and unhappy.
When she eventually stopped trading on Sundays, she found her sales and profits remained steady.
"Our customers just made sure they came when we were open," she said.
"There was no benefit for me in Sunday trading, only extra cost."