We're really diverse, but not really by choice. We have some at Vanguard, Fidelity, TIAA, Nationwide and Questrade, plus bank accounts at 5 banks. For us, this complexity comes from two things 1) we have some work accounts that we can't move (403b and 457b) until we quit and 2) we recently moved from the US to Canada. Once the dust settles -- once we both leave our jobs and settle into Canada, I suspect we'll still have a couple brokerage accounts (maybe 3 instead of 5) and a few bank accounts (because we'll have both USD and CAD accounts). Generally, I favor simplicity, but our crossborder situation requires at least some diversity.