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.
How to tell a person's age 2
Another method that I have thought of for telling a person's age is to buy them a digital photo frame. Explain it to them, if necessary, and set it up. Pay a visit in a week's time and see if they are using it. If not, then you can be fairly sure they are over 60 and don't like the thought of wasting electricity in that way.