I’ve run 1024 since 1992.
800 might be reasonable limit based on today’s tiny pocket screens.
I think we have moved on to 4k for archival stuff.
I'm running 1280x960 as I type this. That image as posted is 1600 x 1200.
IMHO, width of a posted image should not exceed 800. Having to horizontally or vertically scroll a posted image ruins the images's effect.