Since posting this I did a few experiments. Here are the results:
1) I rendered the 25fps graphic out as a uncompressed avi file and dropped it into an AE comp. Then, I made a copy of the video and brought that into AE but interpreted it as 29.97. When compared to the original 25fps clip, it's definitely shorter, assuming it has to speed it up to compensate for the extra frames that aren't' there.
2) I went back into the original AE project file and under the Composition Settings, changed the pre-set from 25fps to 29.97. This seems to have changed the fps but have absolute no effect of the length in the original comp. Now, when I compare this clip (now rendered at 29.97) it is the same length and speed as the original 25fps.
On the surface this seems to have solved the issue of uniforming all the clips to the same fps without altering the speed or duration.
Not that I'm complaining, but I am curious as to how/why this worked.
Premiere Pro's YouTube preset is outdated, 24fps is not optimal for youtube. The best thing you can do is give youtube the highest framerate you can. At the moment, your upload will be converted and played back at 29.97. However, whatever you upload is stored and used as the source material as their system changes (Which it does constantly.) So if your source material is 29.97, upload at 29.97. If it's 60 and you can swing the bitrate, upload at 60.
Also, don't fall for the myth that there is a 'YouTube format that will not be re-encoded.' Everything you upload to YouTube will be rencoded using your upload as the source. So just give them the highest bitrate, original FPS format, so they can do their thing.
Rest of the Question
I can't quite work out what your worflow is from reading your descriptions. But there is one general rule of using Creative Suite, you should not have to have any intermediate encodes. If you are encoding something and then re-importing it into a PPro or AE composition, you're very, very likely to be doing something wrong. Do you reckon you could describe your workflow in steps?
The best thing you can do is give youtube the highest framerate you can.
I disagree. The best thing you can do is give YouTube a file whose frame rate matches that of the source media. The worst thing you can do is change the frame rate from what it was to something new.
Youtube does seem to do well these days with high FPS media. My AVCHD 1080/60p files, edited & encoded to a 1080/30p MP4, looked choppy at a youtube-default 360p, but played fine at 1080p.
Youtube does seem to do well these days with high FPS media. My AVCHD 1080/60p files, edited & encoded to a 1080/30p MP4, looked choppy at a youtube-default 360p, but played fine at 1080p
You seem to be confusing 360p and 1080p as the "framerate"
Good point... my 60p files are presumably 60 full frames per second. I was assuming Youtube is doing 30 full frames per second when they say 360p or 1080p. But I was also kind of missing the point and thinking of it as a file size or bandwidth issue, given that 360p would be less data than 1080p.