I can usually predict whether paycheck parking will stick in a household by asking one question, and it isn't about income or rates. It's this: do both of you understand it, or is one of you running a system the other one tolerates?
Here's why it matters so much. This strategy looks alarming from the outside. The checking account runs lean on purpose. A line of credit carries a balance on purpose. To a spouse who never got the full picture, that looks less like a strategy and more like debt trouble, and they're right to be alarmed, because carrying line balances with no plan really is trouble. The difference between the two is invisible unless someone shows you the plan.
So show the plan. Not a lecture, a demonstration. Walk through one month together: here's the paycheck landing against the line, here's the interest we were paying before, here's the number now, here's why the old way was so slow. Then make the skeptical spouse the auditor. Give them the monthly review, the balance trend, the veto. Skepticism is a feature in an auditor. The partner who was suspicious of the system becomes the one guarding it.
I'll concede this openly: if your spouse hears the whole plan, understands it, and still wants no part of it, that's a real answer. A strategy that needs both spenders to cooperate can't be run by one. Half a household parking while the other half spends freely produces exactly the creep that breaks the math, plus resentment, which compounds faster than interest.
Agreement made once isn't agreement maintained. People forget, budgets drift, and a system nobody talks about becomes one person's private project again by spring. The fix is the same boring answer as always. A recurring look at the numbers together, on the calendar, short enough that nobody dreads it.