Starting from morning onward, the line for PP starts building quickly. The average wait for PP during the day is around 45 minutes. Less than that is a good wait time. So 30 minutes or less is great.
If you can be one of the first in line in the morning, terrific! If not, wait until later in the day when you can invest the time. For example, if you can eat lunch while waiting in line, that takes care of two things at once.
One of our favorite ways to do PP is to make it our last ride of the night. Get in line about 10 minutes before park closing. Enjoy the pretty lights in FL. Enjoy a snack in line. Then exit the ride to a closed park. Main Street stays open an hour after park closing, so do some shopping if you'd like or stop at Market House/Starbucks. Then bid "good night" to DL -- magical!
There is an alternate viewing room for the subs to the right side, toward the Autopia side. Before you get in line, ask a CM where to go. You will be directed to a separate line (there is hardly ever anyone else waiting). A CM will let you into the room. There is bench seating where you will view the sub window on a screen while you hear the narrator audio. Sometimes you have to share the room with other guests. If this is a problem, tell the CM. You can wait for the next round.