A bit of context: my primary use case for Premiere Pro right now is I download the VOD from one day of streaming on twitch (which is usually 6+ hours long), take one "match" from it (which is 30-60 minutes of footage), then edit down that 30-60 minutes into about 10 minutes of highlights.
The issue is... the preview is laggy for long VODs (even if I only have the 30-60 minutes long match left in my sequence). If the original VOD is about 3 hours or less, I have no lag in the preview. Anything above that and the lag starts to ramp up, and it's worse the longer the VOD is (at 6 hours and higher, it gets very noticeable).
Pre-rendering the 30-60 minute sequence seems to fix it (or just exporting it, and then editing that instead of the original footage), but I have to wait 1-2 hours for that 30-60 mins to pre-render.
I will mention I am running an Nvidia RTX 3090 GPU, with an AMD Ryzen 5950x, a high-speed nvme ssd, and 64 GB of high-speed memory on my workstation, so hardware really shouldn't be a problem (all properly configured, hardware encoding enabled in settings etc). Another thing to mention is that source material I work on (as downlaoded from twitch) is 1080p, 60fps, "H264 - MPEG-4 AVC (part 10) (avc1)", that might be relevant.
Is this behaviour intended? Does it occur for other users? Is there any way to fix it?
Anything other than say 23.976, 24, 29.97, 30, 59.97 is suspect immediately. Especially something with an odd number following the period. Like, in your case, the 59.842.
There isn't any 'normal' media with that set of final numbers.
Premiere has problems at times with multi-hour sequences. It has problems at times with VFR, which your media definitely is. And your combination of multi-hour sequence plus VFR is pushing Premiere over the edge after a while.
Either getting the source material exported in a constant frame rate (CFR) format, or converting via HandBrake would help. In Handbrake, on the Video tab make sure to:
1) click in the CFR button;
2) set a specific number in the framerate box above the CFR button;
3) and set the compression to "near placebo" to avoid re-compression issues.
If you can run that while you're away from the computer or overnight, you don't have to sit waiting for it. And Handbrake can run a batch process, though the procedure for doing so is a bit odd to puzzle out at first.