The phrase "if not often" is correct and usable in written English.
It is often used to indicate that something does not happen frequently. For example, "We usually meet on the weekend, if not often throughout the week."
Mr. Romney has proved himself to be a disciplined — if not often inspiring — speaker during the last six years.
The children are accustomed to olive oil, mussels, garlic, oysters and camembert, if not often to lobster.
He could bat, devastatingly so if not often enough, turning games, and he bowled lissomly fast and enthusiastically.
The scale of the recent devastation has been slow to register in the wider American imagination, partly because infrastructure damage has made communication difficult, if not often impossible.
Professor Goldberg said that sodomy laws, even if not often enforced, had the effect of labeling gays as "criminals who deserved unequal treatment".
If not often that you see a play that feels as if it's genuinely thinking out loud, having a dialogue both with itself and the audience at the very moment of its enactment.
My clients die in hospitals as often, if not more often, as they do in vacant farmhouses or elsewhere in the community.
"Cymbeline," once considered a problematic play, has in the last decade or so emerged as a regular staple of the Shakespeare canon, appearing on major stages almost as often — if not more often — than the traditional favorites.
This may be true, but as often if not more often, the player who's being shot at is afraid to leave cover.
The man, a New Yorker since 1977, smiled as if he had not often heard that.
But CD patients are not often, if ever, cured by such treatments.
