"You were travelling on a spaceship you dialled nine chevrons to get to and you're convinced what you saw was definitely your future?"

John scrunches his face, gives a half shrug.

"I mean maybe it was, but they weren't on a Natha ship when you met your descendants something changed, or else maybe somehow you travel back. Did they mention this? Your future self? I figure not, and maybe you just never told anyone about it, but who knows right? Even if your lives start the same, one choice can make a difference. Wait for back up or don't, accept help or don't, go through a gate or don't. There can be like -- split offs at any point, the whole butterfly effect thing. Maybe this... episode was insight, like you say. Maybe not! Maybe it's some Natha thing. Maybe it accelerated for a minute and now it's undone completely! The future seems like something that isn't worth betting on, no matter how much you think you know."

At least, in John Sheppard's 'professional' opinion -- and having watched Back to the Future multiple times, time travelled, fallen into parallel dimensions and befriended a so-called Prophet he's developed plenty of opinions on the whole thing.