For follow-up discussion and general commentary on the topic. Comments are sorted chronologically.
Jack Gutknecht
John MacArthur has a quote on Colossians 4:7 -- Tychicus "never achieved prominence, but he served in an important capacity as Paul's liaison to the churches" — i.e., a real-life example of the wise, gracious conduct Col 4:5–6 calls for.
Also, about Colossians 4:7, Tychicus's arduous journey (MacArthur: crossing Italy on foot, sailing the Adriatic, traversing Greece, crossing the Aegean, then ~100 miles on foot to Colossae) is a living illustration of someone who "bought up" the opportunity to serve, carrying Colossians, Ephesians, and probably Philemon.
We, too, are to "buy up" opportunities to serve (Colossians 4:5) which says,
Mounce, the Greek scholar, says this about "buying up": to buy out of the hands of a person; to redeem, set free, Gal. 3:13; 4:5; mid. to redeem, buy off, to secure for one’s self or one’s own use; to rescue from loss or misapplication, Eph. 5:16; Col. 4:5