The phrase "and so frequent" is correct and usable in written English.
It can be used to describe something that occurs often or repeatedly, typically in a context discussing frequency or regularity.
Example: "The meetings were held every week, and so frequent that it became difficult to keep track of all the discussions."
Alternatives: "and very common" or "and quite regular".
Why, despite failures so great and so frequent, have we not changed the model?
But Romney's transformations have been so sweeping, and so frequent, I'm not sure that there's any core.
Such a natural was he on television panel-quizzes and talk-shows, and so frequent were his appearances on them, that he became known as "Chat-show Charlie".
But among the indigent, the traumas are so terrible and so frequent, says Miranda, that searching for the depressed among them is like checking for emphysema among coal miners.
The error is "so great and so frequent that clinically significant untoward effects can be anticipated".
Clash of clans is an online multiplayer game and so frequent playing of this game would not be advised if you're using an iPhone without an unlimited internet plan and Wi-Fi connection.
Though Wascom's prose is less resonant, he will be compared to Cormac McCarthy — his novel is rife with biblical overtones, laconic psychopaths and violence so frequent and exaggerated it becomes a punch line.
It has strong language and explosions, carnage and destruction so frequent they could come from a cable channel devoted to such displays.
Moments of invisibility and changes in camera angle make it occasionally difficult to control the boy, but the game is so simple and checkpoints so frequent that frustration isn't an issue.
If climate patterns play out as expected in a warming world, they say, winds will be so strong and storms so frequent by late in this century that conditions will "become unfavorable for dynamic soaring flights," on which the birds rely.
"They're not so thorough and they're not so frequent and unfortunately this is what happens.
