Howdy! Show times vary depending on park hours, estimated attendance, and such. Most shows have the same show schedule for at least a week, and sometimes longer. Universal now prints show times in the park maps, under show descriptions, and maps will be changed out according to seasons (attendance-wise: lots of people vs fewer people). The shortest I've seen for the maps is, switched after 3 days

but others can be weeks with the same schedule.
Howeer, let me help with some of the things that have been happening lately.
Extreme Ghostbusters, is a no brainer for me

and one of the shows that rarely changes.
During the Summer months (and other busy times), they have 5 shows:
11:30AM, 12:45, 2:00, 3:45, and 5:00. Sometime in August, the remove the 11:30 show, however the other show times remain the same.
The Graveyard Revue is sort of tricky, because the changes are for pretty much every show depending on park hours. Because this show can be performed in the evening, you may have a show pretty late (after 8:00), or during "regular park hours" (9 to 7), the last show is at only 4:30. However, the first show is usually 12:30 or later, I believe.
Earliest times I've seen shows like Street Breakz, Blues Brothers, and Horror Makeup Show is 11:00...however, if it's the regular park hour (9 to 7), first shows may not be until 11:30 or 11:45. If later park hours, there will usually be later shows of Street Breakz, and Horror Makeup Show. Street Breakz sometimes gets relocated for their "after usual hours" shows...in Hollywood, rather than New York.
I know, it's confusing...but good thing: Horror Makeup Show is usually only 45 minutes in between shows. That's usually consistant.