The frames already lived in Figma, at 165 by 210. The file the team needed was twice that, 330 by 420, and it had to be AVIF. PNG was only the step in the middle.
I did not time a full day of it. I wrote down the steps once the file is already open: export at 2×, convert to AVIF, name the file, upload it. About a minute. For 5,000 frames that is 5,000 minutes, about 83 hours. The set has been updated more than once, so doing that by hand again would be another 83 hours.