I think it depends on how good you, or your partner, are with money and also how long you've been together (trust and knowing somebody well). With my ex, she was very good with money so easy no brainer to just lump all in and have one joint account. She earned less than me but after the bills came out we budgeted for the month and if we had anything spare and we wanted something for ourselves, we'd just ask each other. I had no issue in knowing that most of that spare money was mine. If you or the other person aren't the most responsible then yep, keep what is left seperate.