Oh for the Glory Days!
Job's summing up 'for the Defence' takes him back to the past. Days when the sun shone and the family worshipped him; how he helped the poor and anticipated a great old age as people hung on his every word.
Whether this is to teach his friends what they don't know, to remind them what they seem to have forgotten or simply day-dreaming or fantasising depends on how you read it. One way is to see it as a summary of what in extremis matters to Job and then ask yourself what is missing.
Did family and friends matter more for the warm feeling they gave him than for what he gave them? Did their withdrawal and silence when he appeared signify respect or fear, and did Job ever question which? Think of a tough manager suddenly turning up at the coal face, and notice that now when Job gets their attention it is the wrong sort (chap 30). And might the fact that none of them fall over themselves to come to his aid say something about the relationship and (worse) how Job really feels about them.
On one reading Job comes across as a very self-centred man. As long as everything went well and ministered to his ego all was fine. When it didn't the question was not 'where have I gone wrong?' but 'what has gone wrong with God?' Perhaps what we see here is that the 'god' he had pinned his life to is too small and when it let him down he had nothing, few friends and nowhere to go. If so, he needs somebody to open his eyes, but very gently. He is a wounded man and his three friends are not even in the starting blocks.
Job may have believed all the right things, done all the right things and avoided all the wrong things but closer examination of his self-defence suggests that there is a whole piece of him and the world he has lived in missing. See if you can identify it and what might it say to him and to his friends, to us and ours?