The concluding, twenty first, chapter of Mirkheim recounts three conversations:
Eric with Falkayn;
van Rijn with Sandra;
Adzel with Chee Lan.
After Mirkheim, there is a period, with no stories set in it, when David Falkayn runs Solar Spice & Liquors and Nicholas van Rijn travels around in Muddlin' Through, a total role reversal except that:
van Rijn is not trade pioneering but repairing the damage caused to the Polesotechnic Leagueby its recent civil war;
he is not accompanied by Adzel or Chee Lan - they have returned to their home planets to prepare against the times to come, for which they will often confer with each other.
During this period, van Rijn and Falkayn transfer records from Earth to Hermes, thus providing material for the later Earth Book Of Stormgate (see also here).
Next there is a period when:
David and Coya lead the colonization of Avalon;
van Rijn (we think) leads an expedition outside known space, possibly accompanied by Sandra who would by then have been succeeded on Hermes by Eric.
"Wingless," (see also here) in which Nat Falkayn remembers Ythrians visiting his grandfather David in Chartertown, is set towards the end of this further period but presents the perspective of a young human Avalonian visiting an Ythrian choth. We do not see David or Coya on Avalon.