We have maintained separate bank accounts, and we always tended to pay depending who had the money - a very loose arrangement.
Mrs Hughes sorts all financial arrangements, booking holidays, tradesmen, etc. I am perfectly capable, but she is a bit of a control freak so if she does it, she knows it's done how she wants it, which is fine.
Mrs H's mum is utterly clueless, never paid a bill in her life and since her dad died, we have had to take over the running of her house for her.
Happily, all our daughters can run things if they need to, I think they have a similar system to ours.