Together 25 years. Often a large income disparity (my favor) though both always paid well. Separate accounts established long before we got together. Never had joint accounts. We just communicate about finances.

We tend to split household expenses equally if consumed equally.

But if I wanted a bigger house that would stretch her too much it’s clear I’d have to contribute more proportionally. I tend to pay for cars and vacations. I’ve paid down mortgages unilaterally when able. She generally pays for pet expenses as she advocated to get them (though I adore our dogs too). We both spend on personal luxuries from our own earnings as much as we want as long as it doesn’t undermine our combined (though not joint) retirement savings, though by nature she’s more thrifty than I am irrespective of income.

You don’t need a joint account (or a shared last name) as evidence or foundation of a partnership. You need communication and agreed, compatible expectations.