In general we share income 50/50. Bonuses go only to the individual, stock options go towards retirement. We hold accounts for retirement and shared expenses as well as accounts for ourselves and the kids. Retirement and shared expenses are paid first, DW and I split the rest, and the kids get/used to get a split of that as well. We have an adjustment for car mileage since we ended up driving much different distances to work. Most of our living expenses are shared, though car expenses are paid only as a fixed rate per mile. After that, it's spend what you've got in your individual account. I tend to go for the expensive cars and audio gear, so DW's balance is higher than mine.
We've done this since we got married, 30 years ago now. We consult for all out of the ordinary common purchases, but buy stuff using our own money at will. I've even borrowed from DW in the distant past to buy a new car and made monthly payments with interest.
All the retirement money is considered common, regardless of whose name it is in. We've continued to add to our individual accounts while DW is still w*rking (I told her to quit years ago, but she still enjoys it). After that it'll pretty much be 4% rule with the individual accounts for individual spending. Though we can go for years without spending anything like that much. Since they are not in the main retirement plan, they also act as a margin of safety and long-term care self insurance.