I highly recommend you stop recommending Primer when time travel is brought up. The movie is better viewed not knowing anything about it. It could be a character drama before the weird shit starts going on. By the way, this is an awesome timeline http://neuwanstein.fw.hu/primer_timeline.html
I'm one of those few people who completely hated Primer. I found it to be masquerading poor narrative as intellectual mystery. It's possible to present an intricate, complex logic puzzle as story without being totally incoherent, but Primer doesn't even bother.
For a movie that matches Primer in everything it does right, but none of what it does wrong, check out Timecrimes (Los Cronocrimenes). It is far superior.
I agree! I Loved that film. Especially given the fact that it was made for so little. Huge fan. If you haven't seen it and are willing to put the intellectual effort in, buy it and watch it.