So, how far ahead are you going?
4 seconds sound clip from the Back to the Future movie soundboard.
You can hear this line at 01:45:32 in the Blu-ray version of the movie.
Quote context
[...]
- I never got a chance to tell you.
- What about all that talk about screwing up future events? The space-time continuum?
- Well, I figured, what the hell?
- So, how far ahead are you going?
- About 30 years. It's a nice, round number.
- Look me up when you get there, all right?
- I will.
[...]