The phrase "are frequently set" is correct and usable in written English.
It can be used when describing something that is often established or arranged in a particular way.
Example: "The deadlines for the project are frequently set to ensure timely completion."
Alternatives: "are often established" or "are regularly determined".
The methods of ethnography and cognitive psychology are frequently set in opposition to each other.
When stock awards are tied to benchmarks in a company's share price, the targets are frequently set so low that only a catastrophic failure would prevent a chief executive from reaping the reward, shareholder rights activists say.
Gestures are often overzealous -- talk of the sun, moon or stars is usually punctuated by pointing to the sky; a mention of the heart is sure to be met with a grasped chest -- and voices are frequently set to high.
The playa (ancient lake bed) at the desert's southern end has served in recent years as the site of turbojet car races in which world land-speed records are frequently set and broken.
The works of City Ballet, which has the widest musical repertory of any ballet company in the world, are frequently set to music, often difficult, that is most often heard in concert halls, rather than to scores specifically written for ballet.
In traffic surveillance systems, cameras are frequently set up on islands or shoulders of roads.
They were frequently set polyphonically (in part music) by composers from about 1400 onward.
More needs to be done, however, because only five UK cities had 2050 targets in place, and targets were frequently set for shorter timeframes.
The system was expensive, and it was frequently set off by players who had metal eyelets in their tennis shoes or metallic fibers in their rackets.
His fiction is frequently set in Germany during the war and in its aftermath, an ashen land of the lost and the displaced.
Prior installation of a novel system of dynamic controllers the Rio-Niterói bridge was frequently set into vortex-induced oscillations by cross-winds of relatively low velocities.
