Is Narayan Bali required even after many years have passed since the death?

Yes. The Garuda Purana does not set a time limit after which Narayan Bali is no longer needed or effective. A soul trapped in Antariksha remains in that condition until Narayan Bali is performed, whether that is one year or fifty years after the death. In many families the need is discovered only when persistent Pitra Dosh effects prompt investigation into the ancestral history. Performing Narayan Bali in such cases is still fully effective, and the offering channel can be restored even after long periods of the soul being trapped.