So far all eternally carrying mothers clock has started ticking again (last 2 unless my last original villager (she's JOAT) gets pregnant (she's apparently somewhat popular amongst male parents but so far she hasn't got pregnant again)) and apparently babies have born but no idea what happened to few mothers since they aren't on mausoleum.

looks like it if mother ends nursing baby eternally she carries baby 1-2 weeks if she gets Grant Youthed while nursing eternally but sometimes it really goes close if nursing ends before mother dies.