What extensive break-in does is reduce the duration that IR persists. I've got almost 2,000 hours in my 65VT60 now and stuff that used to take days to get rid of is now gone in a few hours. I expect that as the pixels continue to wear, IR will continue to shorten in duration.
Can confirm with 1400 hours on 60ST50 the same has started happening. Less hours and more 40-60 minutes.