From what I have seen, it takes a while for a line to build.
We were there in October. RD did SDD, then over to AS2, then had a 5 minute wait for TSMM.
when we left TSL, AS2 was about 10 minutes, TSMM was 20 minutes and SDD was 120 minutes.
Haven't done it during EMH. i would expect you should be fine during that time. Most will be trying to ride SDD.