There has never been a time we kept our finances separate. I have been a stay at home mom for over 11 years, and from the beginning our finances have been combined. With only one income (for the most part), this was the only way to go.
I suppose if we had started out as a dual income family things might be different. I did (and do) most of the shopping for the family, and he earns the money, so separating the finances never made sense.