I’ve burnt for years and absolutely build ultra hot fires occasionally to get ride of creosote build up but eventually like you say will get ash build up which can burn or eventually just plug the pipe. You would need access points to use a vacuum because the article showed these things zig zag back and forth to make the heat travel around the bricks. Maybe it just takes years and years since the article claims you only need to burn for a couple hours a day where my wood stove burns all day.