I'm afraid it's a rather long story.

我恐怕这是个相当长的故事。

《柯林斯英汉双解大词典》

We have known each other for a rather long time.

我们已经认识相当长一段时间了。

youdao

Two little old ladies were attending a rather long church service.

两个小老太太在教堂做礼拜，很久都不结束。

youdao

He says circumstantial evidence indicates the launch involves a long-range missile rather than a satellite.

VOA: standard.2009.03.12

It seems to me rather a long distance from the thought, nobody can die for me,nobody can take my part, to the claim,everybody dies alone.

对我来说，没有人能够代替他人死亡，这说法离每个人都是孤独而死这说法，还有好一段距离。

耶鲁公开课 - 死亡课程节选

One of the big arguments that is part of this story is when did this development of new way of fighting come about; rather quickly, over a matter of a few years, or did it stretch out over quite a long time.

人们对此最大的争议就在于,这种新型战斗方式是何时为军队所用的,是在短短几年内迅速发展起来的呢,还是在很长的一段时间逐步形成的呢

耶鲁公开课 - 古希腊历史简介课程节选

They're showing off a rather long, elaborate demo of Dead or Alive 4 for the 360.

ENGADGET: & Joystiq's live coverage of Microsoft's Xbox 360 E3 event

If you are going to grow it, it is a rather long-season plant, clocking in at about 112 days from seeding.

NPR: The Vegetable World's Ugly Duckling: Celeriac

Although Earth would be a rather long way to go for lunch, the argument is that the decision to take such a risk is not one for a handful of scientists.

ECONOMIST: An argument over whether to send messages to aliens