Purpose of dbt being idempotent for when data grows large

This is possible if you take advantage of the {{ this }} variable, as described here. In short, as long as you have a reliable high-water mark in your table, you can do something like
where src.id > (select max(id) from {{ this }})
instead of a hard-coded window.

On the limits of incrementality is another good post as a chaser to your original link. And as @josh says, occasionally doing a --full-refresh is a way to clean up if you have very late arriving facts that you care about.