Joseph is (almost) never serious though he pretends to be…
If this question is still relevant to anybody I’d suggest setting up X dollars (whatever amount you think is reasonable) as an automatic transfer – each month – to a savings account, and putting the spender (HIM OR HER) in charge of paying the bills.
But first have an open discussion about it and get your spouse on board with your plan – and the details. Compromise on the savings amount if necessary.