Please help me understand Golok

What I knew since childhood is that Narayan and Lakshmi were born as Ram and Sita in Treta yug, then Krishna and Radha in Dwapar yug..and they return to Vaikunthya when their Leela is over.🙏🏻 I recently learnt about Golok where Narayan and Lakshmi live as Krishna and Narayan avataar forever. Can anyone explain this or direct me towards scriptures or books where I can understand this better! Radhe Krishna🙏🏻