I would agree vouchers should have priority over points, not because expiration only but as they are achieved via loyalty, not Cc spend. And when loyalty is achieved via revenue, to my math there is still substantial difference on revenue per earned voucher vs points.

Using 1% commission as baseline, not thinking in avios as I have not yet learned to do it, J upgrade is achieved with 20ke spend/year, bringing in 200e of revenue. In revenue based model to get one LH voucher, one needs to bring at last 5k direct revenue. But of course plat has effectively 3 vouchers for 9k -> revenue/ voucher is 3k. So, voucher should have 10x power on upgrades. But of course there is other side on loyalty so 10x is of course just math and not taking into account anything else.