Yah...u seem have some good point.Just a normal logical point.
Lets Take eg.Tumbuhan seperti rambutan,belimbing,durian etc.
When they are ripe,they will drop one day too.Be it eatern by u , animal or insects.
As for human,once they are being employed,at first ,they are so hardworking ,a good listener wan,etc.After for severals months or after increment,they start to begin unproductive.If they are happy with the increment,they are happy with the boss,then it is okay.But sorry to say,majority is the opposite wan.
Some employees come to work and treat the employment as "Jambatan" to get money to cover urgent need and would move to his desire (actual need) when time comes.In that way,who/what do u expect from them in term of performance etc.
Think carefully

If they got this kind of attitude no matter where they go they are stuck with it. Even if the place is just a stepping stone for future planning, at least act accordingly. Ppl will not say bad thing if its not happening.