Since it's March and probably means graduation, I did a calculation about at which age casters graduated, considering just the ones who leaved on the WeatherNews LiVE era (that started from April, 16th 2018)
https://www.timeanddate.com/date/duration.html
Using link above (including end date in calculation), the oldest caster who graduated were Izumi 1st (30y,6m and 21 days) and Saya 2nd place (30y,5m and 2 days)
The youngest were Rina 1st (25y, 4m and 28 days), Ayame 2nd (25y and 7 months) and Non 3rd (25y, 9m and 5 days)
So, if my calculation could have some truth in it (but I don't think that's a rule about a graduation's age limit) I would add Yui (being close at age 30) to names made by >>/2532/ (though I think chances of her leaving the company are next to zero)