In drafts for Appendix A Tolkien wrote:
'And the line of Dain prospered (...) the name of Durin, and he returned to Moria; and there was light again in deep places, and the ringing of hammers and the harping of harps, until the world grew old and the Dwarves failed and the days of Durin's race were ended.'
CJRT notes:
'It is impossible to discover whether my father did in fact reject this iea, or whether it simply became 'lost' in the haste with which the Appendices were finally prepared for publication. The fact that he made no reference to 'Durin VII and Last', though he appears in the genealogy in Appendix A, is possibly a pointer to the latter supposition.' The Peoples of Middle-earth
See also the abandoned
Epilogue on this matter.