Ok this is going to be my first post here, but I have to bring up this theory as I had to miss the live show version of the Lake House after previously having tickets.
I think that Jason's "Jacob's Ladder" version of this movie was hilarious, but did not go far enough...
If this movie is a "Jacob's Ladder" scenario of anything, its from Speed. Making this movie the ACTUAL sequel to the original movie.
Let me explain my crackpot theory:
Keanu & Sandra actually crash horrifically once escaping from the bus on the tarmac at the airport. (Spoilers for the movie Speed)
After that point, the rest of the movie is actually Keanu's "Jacob's Ladder" scenario where he tracks down Dennis Hopper and saves the day. Its short and relatively simple, fitting Keanu's character in the movie.
The Lake House is actually the longer more drawn out version of Sandra Bullock's "Jacob's Ladder" scenario.
In this version, the movie plays our so incredibly slowly thanks to Sandra wishing she had more time with Keanu from "Speed". They can't just meet and fall in love, because in her near death state in Speed, Sandra just wished she had known Keanu for longer than a few hours. Everything in this movie requires constant waiting.
This is exactly why the dog is named "Jack" as it is the only character to play a big part of both of their lives.
Her mind knows that this is all fake, which is why Keanu gets killed by a BUS! Just like the bus that killed them both, setting forth these two dream states.
Coming together in that final moment near the mailbox is where it comes to and end for both of them as they are now finally dying as their original characters in Speed.
Yes, this was a crackpot theory. But it makes far more sense than the actually move did.