We have a single example (used twice with slight differences) that demonstrates use of @notAfter to indicate the imprecise end of a duration; however, @notAfter is not intended for indicating a duration.
<residence from="1857-03-01" notAfter="1857-04-30">From the 1st
of March to some time in April of 1857.</residence>
See thread “bad date example” on TEI Council mailing list, starting 2015-05-25.
I thought we decided in the discussion that there was nothing wrong with this?