I still have mine in all 7 cities. I suppose it becomes less useful as one ages up and acquires more special buildings that produce goods and produce/boost supplies, but since supply production generally lags way behind coin production I figure I can use all the supply boost I can get. I would say for newer cities it's a must-have.
Get back to me in another Event or three, I may delete it to make room.
Early on it is very good to have. but soon it becomes somewhat useless. Ony later, depending on play style. again become essential
If you early on get a Himiji Castle, then LoA becomes less significant.