It is correct and usable in written English.
You can use it to describe a particular period of time, for example: I spent a lot of time in the library mainly during the summer months.
It is based on "The Arcades Project," Walter Benjamin's portrait of nineteenth-century Paris, assembled mainly during the nineteen-thirties.
However, they contribute to our work mainly during evenings and weekends, outside their formal social work professional activity".
Seeing him standing there, Valenti, who had known Lyndon Johnson mainly during his Vice-Presidency, was startled.
But it was a Saturday night, the Monkey Bar hops mainly during the workweek, and the place was empty.
Summers are hot and winters cool; precipitation is moderate and falls mainly during the warm months.
The couple rent out the house for about 20 weeks a year, mainly during the summer.
Buddhism was transmitted into Tibet mainly during the 7th to 10th centuries.
"Let's Cool One," reconceived as a waltz, similarly comes alive mainly during Mr. Strickland's shift.
Streamflow occurred mainly during winter.
There are, however, also larger differences mainly during disturbed times.
PP should be expected mainly during childhood and pubertal age.
