This is my favorite scene in Primer. It has so many classic elements. When you watch this film for the second time, you start to realize how complicated events have already become.
Aaron’s impulsive use of the time machine, his making a copy of one of the boxes, and putting his former self in the attic have set the stage for a great escapade.
"I was going to give you this big speech about how we’ve been friends for a long time and built up trust and that whole big thing ... but how about this instead." Abe implies that his last approach didn’t work. He knows that Aaron is impulsive.
Abe hopes to try a new approach, teaching Aaron about the box, giving him a few rules about its use. Abe has already built both boxes. This is not his very first trip. Note how Abe is confident that they will see his former self appear at the U-Haul. Later, he shows his experience with his knowledge of the static shock that Aaron experiences.(Again, Aaron may merely be repeating his mistake to avoid altering what occurred the first time Aaron traveled with Abe through the boxes.)
It quickly escalates to having Aaron(1) in the attic. Aaron(2) has his own box. Are there a lot of steps in between, not shown to us? The number is nearly endless. Aaron(2) may have followed Abe’s rules, allowing Aaron(1) to run around undisturbed. This could have led Abe to figure out what was going on and use his fail-safe to reset the timeline. If this happens, Aaron(2) can use his fail-safe, not only going back farther, but erasing Abe’s knowledge that Aaron(2) is already on the scene. In this case, Abe would not even know that he used his fail-safe at all. Such is the luxury of possessing the primary or earliest fail-safe. If Aaron leaves an 8 hour gap, then Abe would never arrive until Monday morning at the earliest. That would allow Aaron to exit his box on Sunday evening and get a good night’s rest. Then, he can calmly proceed to the park bench and begin the day anew.
