They have been providing the help you weren't here to give me - 1 Corinthians 16:17
Paul made a practice of giving and receiveing appreciation
He took time to praise Stephanas, Fortunatus, and Achaicus - Corinthian believers who traveled out of their way to encourage and assist Paul in his ministry
This was important enough to Paul he didn't just suggest that people show their appreciation - he commanded it
Paul: You must show your appreciation to all who serve so well
Why not thank people who make your life better? You will be blessed when you offer your thanks and so will they