For example, there are still open and active claims in case of NextBank that has been shut down in 2002, and had some updates on status done in early 2015, some 13 years later [1]
Personally I suggest keeping 70% of your financial assets in cash in safe at home, preferably split into 20% in low-volume silver coins (80% silver) and 20% in foreign currency (EUR) and the rest in USD.
[1] https://www.fdic.gov/bank/individual/failed/banklist.html
Yes, if you're living during the Great Depression perhaps but your suggest is ludicrous. Maybe a few percentage points in crypto and cash, but most of it should be in your bank/investment accounts.
Meanwhile banks wage war on cash. Its harder and harder to withdraw your own money. Here, try and show up at your bank say you need $150,000. They tell you to come back in few days, and in some cases they will ask you to fill out the form and explain yourself why you want to withdraw your own money.
If you do not live in a reasonably safe neighborhood, plus do not owe an alarm system, plus do not owe a safe, plus do not awe a firearm, then yes the bank is your best friend. Other than that no reason to keep some federal paper at someone's else possession at their disposal for a mere 0.5% per year. You don't gain anything and in some cases, you might lose some or all of it (yes extreme scenarios but always)
Here few articles to continue...
http://dailycaller.com/2014/01/29/bank-refuses-to-give-custo...
http://thefreethoughtproject.com/feds-banks-inform-law-enfor...
http://www.bbc.com/news/business-25861717
and here this one quick very informative read: http://www.rd.com/advice/saving-money/secrets-bank-teller-wo...
ps. in all fairness I would say keep 70% in gold or silver, but over the years this commodity has been shifted between the countries in such huge quantity (government buy/sell-outs), that the price is dictate by which country has specific political system and how much PM they owe, rather than true market price. Unless you can predict you won't need to turn your PM into cash within next 5-10 years, which is hard calculation for anyone these days.
Or maybe invest in some extra firepower?
It's not so relevant here, but in the case that the bank became insolvent (very unlikely in this case), FSCS aims to pay out within 7 days, and will pay all claims within 20 days.