Kpop has “generations” in the sense that mandatory Korean military service for men puts an expiration date on them all being present, and they fade away in popularity if only some of the members are present.

Also, the contracts are long, but idols don’t necessarily stay around if they think they can get a better deal elsewhere, or if they want to move onto another chapter of their life which idol employment doesn’t allow (like dating).

It’s Blackpink, BTS, and Twice now. Before them, it was 2NE1, 2PM, Miss A/the Wonder Girls, SNSD, etc.