I normally check in at 5:45-7:30am or 1-2pm. I do not check in at J or Y, but I have been paying some attention to the check-in situation over there, especially recently. Between 5:45-7:30am, the J line is very short, and there is no waiting from time to time. Between 1-2pm, there are normally queues in J check-in, but are much shorter than Y and the line move quick fast.