The phrase "longer than if" is correct and usable in written English.
This phrase is used to suggest a comparison between two things that are not equal. For example, "My commute time is much longer than if I worked closer to home."
That's longer than if you'd been in prison for murder.
"They're going to remember that a lot longer than if I just bought them something.
If you have a hundred cats, you'll live 10 times longer than if you have 10.
"The duration of the killing may be longer than if a gun was used.
It might take longer than if she picked problems apart technically: 'The trumpets are late on the eighth note.' But she gets a more organic result.
"These people now have the loyalty and commitment and will stay with us longer than if we didn't have the program".
They can rest longer than that if placed in a 150-degree oven after the first 10 minutes.
Forty years in one place, playing one defense, and really it's longer than that if you consider that he was a walk-on player there in 1962.
The Olympics are July 27 to Aug. 12. "Matt's ready to get married in September," Chandler said, "but I told him it takes a little longer than that if I don't start planning until after the trials".
It takes two hours and forty-five minutos to get from Los Angeles to San Diego by train, and a little longer than that if there is a mechanical delay, which on this day there was.
They suggest the gene alteration may hold a key to understanding earlier findings that yeast, flies, worms and rodents live far longer than expected if they are fed very little food.
