I have accounts in 3 different banks...2 checking accts. and 1 savings.

I have checking at a big bank and savings at a credit union.

Well using two accounts is indeed convenient. Think of a situation when you have a loan from one of the banks and you also have your business account there. Imagine you do not have money on your account and the bank is waiting for a transfer to cut the money, but you do not want the money to be cut. You can always ask your customer to transfer fund to another account and so you can avoid money-cutting.

In fact I use 3 accounts for my company: 2 normal (onshore) accounts and 1 offshore banking account from Jersey. It is quite convenient. My country's banking system is quite volatile and exchange rate often experiences large fluctuations. I keep significant amount of cash overseas and it is very easy to transfer them back if needed.

I have used as many as six at one time, but the lower you can get the number the better. At present we use two because one does not offer checking accounts but provides better savings account interest rates. We are looking at several other options to se if we can bring it down to one.