> And if that's the case, the LogEvent objects will end up automatically promoted to OldGen.

Why do you think this would happen? There's no mechanism that makes young gen objects that reference old gen objects (or are referenced by old gen objects) get promoted faster. You have to survive a certain number of collections.

Ah shoot, you're right this wouldn't be what I'm thinking.

I was thinking of "GC Nepotism" [1]. That's the case where an object in old gen pointing to an object in new gen will automatically promote that new gen object into old gen. This can be particularly problematic with graph structures.

[1] https://psy-lob-saw.blogspot.com/2016/03/gc-nepotism-and-lin...