I most often edit 4K GoPro videos and sometimes have rendering "freezes" with a video in the 10-minute range (or longer) length. These videos will have 3 stack video tracks (3 cameras), multiple backgrounds and text (example below). It's not uncommon to end up with 7-9 tracks. The likelihood of encountering a rendering freeze trying to render the entire video is unfortunately fairly common.

My timelines from yesterday

My work-around is to render the video in thirds or quarters and then use ffmpeg to stich the rendered segments to together. It takes only seconds for ffmpeg to stitch the segments (opposed to a longer time if you use Vegas to stich them back together). Note: In the above picture the raw video GX020658.MPR is a stiched video of 4 "chapters" from a GoPro 8 and is now one video that matches the length (track 2) of the GoPro 10 and 11 videos.

ffmpeg is easy to use from the command-line (or a batch file).

To use ffmpeg, I make a text file that looks like this: (here I name it list.txt)

file 'GX012760.MP4'
file 'GX022760.MP4'
file 'GX032760.MP4'
file 'GX042760.MP4'

From the command-line (or a batch file), I issue this simple command:

ffmpeg -f concat -i list.txt -c copy GX012760_merge.MP4

Here's an example of a video I edited yesterday with this method:

I sourced ffmpeg (essentials download) here (ffmpeg.exe is located in the bin folder) https://www.gyan.dev/ffmpeg/builds/

I suggest verifying the .sha256 signature (it was good yesterday 11/24/22).

Conversely, if you want to split a large MP4 into smaller segments you would use this command (here I split a 38 minute video into two 19 minute segments.

ffmpeg -i input.MP4 -t 00:19:00 -c copy output_s1.mp4 -ss 00:19:00 -c copy output_s2.mp4