The phrase "a set length" is correct and usable in written English.
It can be used when referring to something that has a predetermined or fixed measurement or duration.
Example: "The document must be formatted to a set length of 10 pages."
Alternatives: "a fixed length" or "a predetermined length".
Courses run for a set length, with material provided each week.
Forget all-expenses-paid trips for a set length of time, crooners, quoits and dining at the captain's table.
If real progress is to be made, interlocutors for the insurgents must prove that they can stop violence in specific areas for a set length of time for instance, by promising not to set off roadside bombs, the insurgents' main weapon, in a certain district for, say, a week.
Had she known her exact speed, and the exact rate at which the current was carrying her in the direction of the Indian Ocean, she would have been able to answer the question of whether she was about to die by solving a simple geometry problem: a point travels at a set speed at a set angle toward a line of a set length while moving at a set speed to the left.
Start-ups enter and leave as a cohort (starting and ending the program at the same time) in a program of a set length.
Like an accelerator there is no physical office space, and start-ups enter and leave as a cohort in a program of a set length.
This might have worked better as longform TV; a box set length could give the excellent Collette more to do.
In addition, we also considered the fact that gene sets with a large "set length" (defined as the total exon length of its genes) accumulate on average more mutations and for this reason show a lower variance in N/ S rates.
There is no set length for a paragraph.
There is no set length for a strip, though most are usually one or two lines of 2-4 frameachach.
But "In Between Days"'s delicacy of feeling doesn't last, during a set whose length smashes holes in the crowd.
