It's a long time since they left.

他们已经离开很久了。

《牛津词典》

The empty shell of a snail or clam may be left behind, and if it is sufficiently durable and resistant to dissolution, it may remain basically unchanged for a long period of time.

蜗牛或蛤蜊的空壳可能会被留下来，如果足够持久和抗溶解，它可能会在很长一段时间内基本保持不变。

youdao

That was a long time after Hanna had left the city.

那是汉娜离开这座城市后好长时间的事了。

youdao

We still don't have (JJ) Redick. (Christian) Laettner left a long time ago.

NPR: BracketRacket: Zags, Ryan's Wiki And Geno Is 59

The 36-year-old will go into the season with a new race engineer after his long-time partner Ciaron Pilbeam left Red Bull for Lotus.

CNN: STORY HIGHLIGHTS

He said properties left empty for a long time often attracted "vandalism and fly tipping and drag down the value of the properties all around them".

BBC: Derelict house