Our tickets were for the end of June and we booked them 4 mos. in advance.
So, here's what the trend is for booking tickets at the studio.
4 mos in advance for earliest tour time is the 1st tour 9 a.m. (hardly no-one at all)
3 mos. in advance for earliest tour time is 11:30 a.m. (approximately 30 people in line - our wait @ 12:30 p.m. was 15 mins. with the tickets and getting through the 1st set of doors to start the tour)
2 mos. in advance for earliest tour time is 1:30 p.m. (long lines start forming)
If you wait 1 mos before purchasing the tickets, the only times which are available are after 3 p.m. (this is when is it extremely crowded.
I hope this helps.
By the way, there are two cafes, lots of restrooms, great interactive stuff for everyone. However, the extras just like DL and DW is a little pricey.
Our children (DD13 & DD11) absolutely loved it.
I hope this helps!