I've been exporting from within LRT, but I think I might have to stop using this as it doesn't work well with my system.
Quite often my exports result in huge chunks of missing frames. Sometimes this is caused by me using the laptop at the same time, other times I'm not sure. I can't quite control when my laptop turns its screen off, and this seems to cause missing chunks.

To re-export all of my JPGs would take a huge amount of time, and I do have most of them - I'm only missing about 10%.

1. Is there anything I can do now to quickly find and export only the JPGs I need, then make a video of them?
2. If this is not possible, could the export process take this into account and provide the option not to re-export existing JPGs?
3. What would be a better workflow for me? I need to be able to resume or 'fill in' failed exports, basically. Manually searching for missing frames or starting an entire export from scratch each time it fails isn't ideal.

Thanks!

If your laptop goes to sleep while exporting, you'll definitely get timeouts and this will lead to missing frames.
You should turn off or set the sleeping time to a longer value than the export.
Currently you can't just export the missing frames via LRTimelapse.
This is only possible with the LRTExport plug-in in Lightroom.
All in all, the Lightroom export is the preferred way of exporting, it's more stable and has more features.

Thanks for the quick reply! I'll use the Lightroom export from now on.
Cheers!