It's impossible to know what is going on without details of your work flow. Have you ever done this kind of thing before? The estimates in the timeline can be way off if you run into a few frames of something that takes very long time to render like temporal effects or particles. If you are rendering a production master from AE it's almost always best to break that up into smaller bits and then assemble color corrected production master in your NLE for final tweaks, sound mix and render for delivery. Color grading is seldom the last step in a production.
Never exported a feature film with color correction from AE. I am a novice when it comes to exporting a file of this size or the workflow. Are you suggesting that we make segments AE project files or render out video files in segments lossless to put into an NLE?
Our workflow has been cutting the film in Premiere Pro cc 2015, then bringing it into Ae for color correction, grading and special effects (the special effects are individual comps that were done separately, then added to the color correction timeline).
Get a little app that shows your CPU use. If it's only using one core. AE 2015 tends to only one core for rendering.
So use 2014, instead. It will use all cores, somewhat. Not as much as it should, but somewhat, so will be faster, by a good margin, but not as fast as it should be.
AE 2015 is an alpha demonstration of the new renderer, so most of its future potential features aren't yet working.
Not printed on the tin, but should be.
Here's my normal workflow for a movie in the most basic terms. First some definitions. A sequence is a Premiere pro timeline. A shot is one take that has the in and out points set in a timeline. A scene is a section of the story set in the same location with a single main dramatic point to make, an act is a collection of scenes that break the story into major parts like act one, act two, act three or open, introduce the hero, first conflict, hero's decision, turn to close, end.
- Rough cut each scene or each act as a separate sequence in a NLE like Premiere Pro. Usually never more than 10 minutes. I usually break it up into scenes but sometimes into acts. Scenes may be assembled into acts. The sequences are named to match the scenes in the movie.
- If there are portions of the movie that require a huge amount of color grading I'll start the process in Premiere or pre-grade the footage in another app so I have something to work with that is close to a uniform look. IMPORTANT - Don't destructively color correct anything. If you are careful on the set and when you transfer your footage to the post production process the initial grade should give you a DI (digital intermediate) that is suitable for the rest of the project.
- As scenes are completed I assemble the scenes into a final movie in a single sequence. The advantage here is that you will probably discover that you need to change scene 4 or move scene 6 to the beginning of the move to better tell the story.
- As I am working on each scene I send the shots that need effects to AE and unless the effects are extremely basic and it makes sense to use Dynamic Link, I render those effects shots in AE to a production codec and replace the shots in the Premiere Pro timeline. If there is any chance that I'll need to do some more editing to the sequence or make changes I'll give the shots I work on in AE handles (extra frames at the head and tail) so I do not have to redo anything in AE. If an entire scene needs special effects then I will figure out what can reasonably be grouped into a comp and build up the scene because a good scene and even a good movie is recut several times.
- Back in Premiere Pro, many times in the final movie sequence, but sometimes in each scene I'll add sound effects and folly and music to the sequence then send the sequence to Audition for audio polish.
- Back in Premiere Pro I'll run the final sequence through Speed Grade to give it the first pass a color correction. If needed I'll send scenes to AE for special color grading. It's amazing how much you can do inside Premiere or with Speed Grade
- As a final polish I'll go back through the project, make any final adjustments to any aspect of the movie that needs changing, send the entire project to Audition for a final sound tweak, then bring everything back into PPro for export as a Production master. The production master (NOT AN MPEG FILE) is a lossless master copy of the finished movie that is used to render copies for distribution which for 8 out 10 of my last productions has been an MP4 rendered in the AME to the Vimeo HD preset.
If you are intent on color grading the entire movie in AE I would at a minimum, pre-render anything you have already built in AE to a suitable production codec, replace that original footage in Premiere, then break your movie into scenes or acts by dragging the final movie into a new sequence and cutting it up into portions you can color correct in AE. Bringing anything longer than about 10 minutes into AE for color grading as a single project is, in my humble opinion, nuts.