I cook sometimes, but not so often.

我有时候会做饭，但不经常。

youdao

I enjoy going to a disco occasionally, but not so often that it becomes a bore.

我喜欢偶尔去蹦的，而不愿去得太频繁而产生厌恶感。

youdao

Although men flatter themselves with their great actions, they are not so often the result of a great design as of chance.

人常为自己的壮举自鸣得意，但是他们的壮举往往只是偶然运气产物而非伟大构想的结果。

youdao

She often said: "You must never so much as think if you like it or not, if it is bearable or not.

VOA: special.2009.07.26

That they exist is a proof that American ideals are not the tawdry pretenses they are so often accused of being.

或许这类人的存在,正证明了美国式理想并非无可挑剔,或者说它也在经受着现实的折磨，“

耶鲁公开课 - 1945年后的美国小说课程节选

A little indirect but not so indirect that is difficult to understand. You should use this often.

有一点委婉，但不至于委婉到让人难以理解。应当尽量多使用这种句型。

Why don't 课堂 - SpeakingMax英语口语达人

Death and taxes are proverbially inevitable, but they need not so often be synonymous.

CNN: Death And Lower Taxes

Countries with big populations are often politically powerful, but they are not so often prosperous.

ECONOMIST: LITTLE COUNTRIES

The idea is to check often enough so that you are aware of what is happening with your investments, but not so often that you are constantly tempted to tinker with your portfolio.

FORBES: Proactive Buy-And-Hold Strategy