Yeah, I also think decision models for pruning context isn't worthwhile. You're paying to load it into context (of your decision model), in order to save on loading the same data into context (of your generation model). The only way the economics makes sense is if you need a much smarter model for the compaction, but can't pay for it to load all of that context (because it's uncached or something). That sounds like a niche but it really doesn't exist. Cheap models are good enough, and smart models are cheap enough.

Personally, I use a harness extension that auto-compacts my context just before the cache expires. Combined with the default compact-when-full, this ends up being pretty much always what I want. It's one less thing to think about.