The phrase "revolving door" symbolizes a situation where people keep entering and leaving a place, organization, or job very quickly and frequently. Full definition
The majority of candidates don't last, and the two year revolving door of cheap labor keeps costs associated with salaries and benefits low. (defensedenver.com)
This is an expensive revolving door for low income consumers. (think-creditcards.com)
The gates at American prisons can seem like revolving doors. (sciencemag.org)