depends. there was a group called girls' generations (SNSD) that was very popular and they were together for ten years. each girl of that group had went on to do something fairly noteworthy for the most part, either as a radio/tv host, actress or solo singer.
Twice seems more popular at this time that SNSD was but there is more international attention to kpop at the moment then there was 10 years ago. She seems to have an affable personality and is the second best singer in the group so she could end up doing music or acting, I think she's more attracted to music but you never know.
There are some OLD actresses in korea but not a lot of old singers at least in pop music. BoA is the oldest I know of at 32.
So 9+ years as a singer I'd say.