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The most recent WD defs file update that came through WU here was on July 6th:
As you can see, the update frequency interval is between 2 to 3 days; I also haven't installed any of the SHA-2 updates yet; I usually tend to update WD manually, though, due to more frequent updates delivered that way (3 to 4 during a day...).
I guess you could test yourself by leaving WD not (manually) updated for more than 3 days, while keeping WU itself enabled (e.g. notify but not auto-install updates); if nothing turns up after, say, 4-5 days, then you'll get confirmation WU it's broken...
As for previous Vista updates, a more ominous rumour is flying around, that dedicated XP and Vista MS Update servers will be permanently shut down; see the relevant XP thread:
https://msfn.org/board/topic/178377-on-decommissioning-of-update-servers-for-2000-xp-and-vista-as-of-july-2019/
XP die-hards have already started archiving XP updates from the Catalog, Web Archive and elsewhere, for future usage; haven't seen a similar effort undertaken from Vista communities; but I personally think we should be OK until Jan 2020, when both Server 2008 SP2 and Win7 SP1 reach Extended Support EOL; but I might be wrong...