-
Yep, the off-the-shelf ones generally throttle after a while.
The best thing to do is build your own external SSD, using a metal finned chassis to house an M.2 NVME drive, ideally with a dual-role Thunderbolt/USB4 controller.
I have a couple of these with 2TB Samsung 980 Pro drives in them; they get hot but the heat sink chassis dissipates enough for them to never throttle all day long.
Gets 2.7GB/s read/write speeds via Thunderbolt as well.
It should be here (at friend's) Friday. I'm sure you're all excited to hear about it and I now look forward to letting you know every detail.