I will share my last experience with a 2017 F150 3.5 Ecoboost
Just traded it with 228,000 miles. Full synthetic it’s whole life. Compression was good. I did replace the catalytic converters at 200,000 as they had reduced flow.
It had a rattle at startup that I originally thought was the cam phasers. After time I became convinced it was timing chain rattle. I decided it was time to go new as at that point, I figure it had provided the best cost per mile. Got $12,000 trade in and that was that.
My decision was because of the unknown. If I went ahead with the timing chains and phasers, what would be next? I figured the 10 speed transmission and that is a very expensive one. No doubt engines last longer than they use to but at some point, vehicles reach their most economical cost per mile. Determining that point is the tough part.