Yea, though he live a thousand years twice told, yet hath he seen no good: do not all go to one place?

Wesley's Notes

6:6 Tho' he live - Wherein he seems to have a privilege above an untimely birth. Seen - He hath enjoyed no comfort in it, and therefore long life is rather a curse, than a blessing to him. All - Whether their lives be long or short. Go - To the grave.

Jamieson-Fausset-Brown Bible Commentary

6. If the miser's length of "life" be thought to raise him above the abortive, Solomon answers that long life, without enjoying real good, is but lengthened misery, and riches cannot exempt him from going whither "all go." He is fit neither for life, nor death, nor eternity.

Matthew Henry's Concise Commentary

6:1-6 A man often has all he needs for outward enjoyment; yet the Lord leaves him so to covetousness or evil dispositions, that he makes no good or comfortable use of what he has. By one means or other his possessions come to strangers; this is vanity, and an evil disease. A numerous family was a matter of fond desire and of high honour among the Hebrews; and long life is the desire of mankind in general. Even with these additions a man may not be able to enjoy his riches, family, and life. Such a man, in his passage through life, seems to have been born for no end or use. And he who has entered on life only for one moment, to quit it the next, has a preferable lot to him who has lived long, but only to suffer.