I've just uploaded my 150th sermon to my sermon blog Preached Sermons here. There are plenty of audio sermons available on the Internet but nit so many sermon scripts. I began the blog about four years ago and since then there have been over 30,000 hits. Some sermons have had more than a thousand hits. Check it out.
Bonhoeffer uses a similar phrase 'worldly Christianity'. It's J Gresham Machen that I want to line up most closely with. See his Christianity and culture here. Having done commentaries on Proverbs (Heavenly Wisdom) and Song of Songs (Heavenly Love), a matching title for Ecclesiastes would be Heavenly Worldliness. For my stance on worldliness, see 3 posts here.