I do After Effects work for someone who edits in a different office. We use QuickTime movies with the PNG codec (which is lossless at the highest quality settings) to pass movies back and forth. These movies are about half the size of movies created using the Animation codec. It's important to use a lossless codec when passing movies back and forth between post-production applications; I'd be really annoyed if he gave me lossily compressed footage for keying, for example.
There's no problem with mixing frame rates in a sequence, especially if one of your footage items is at twice the frame rate as the other---so the software won't have to do any interpolation / frame blending to create the in-between frames.
Thanks, I just did a test export and 15 seconds of video created a 1GB .MOV file using the PNG codec
I understand the files are not compressed. Do you think they can be any smaller than that?
How long are the movies your associate sends you and approx what do file sizes look like?
> I understand the files are not compressed.
You misunderstand. The files are compressed. But they're compressed without losing any information. Losslessly compressed movies are a lot smaller than uncompressed movies---but they're still bigger than movies compressed with a lossy codec that would be more suitable for final delivery and distribution.
> How long are the movies your associate sends you and approx what do file sizes look like?
I tend to work on individual clips that are from several seconds to a few minutes long. They're usually a small number of GB each. Don't fret about large file sizes for intermediate files. Making movies small matters when you're streaming them for final delivery, not when you're handing over a hard disk or using an FTP server to exchange files for post-production work.