I think American Express' experience is that after X years members are less likely to cancel (no doubt there are other variable). If this is a personal Platinum why not actually cancel and apply for another version?
I'm just going to keep it. I've got 4 total cards under this account and my people like the perks. Esp lounge access. And We've all got a bit of travel coming up where we want the DL club access.
My sense of it is that HUCA isn't going to yield any different results. Maybe next year.