AU to increase available credit and length of credit

[daddyofprecious]

My partner is considering having his father add him as an authorized user on his oldest credit card account. We are hoping to raise his available credit ratio and length of history. We are applying for a mortgage and the loan officer says they don't mind AU on the account. Is this still an effective approach with the new FICO 8 and other algorithms uses today?

[CH-7-Mission-Accomplished]

I can only speak from my own experience, but all eight of my A/U accounts factor into my average age of accounts and utilization.  For some reason the three BofA accounts on which I am an A/U, only report to TU.  Have tried to get them reporting on the other two but no luck.