You are supposed to, but it is only insured to 250k. That might seem like a decent amount but if you suffer inflation and a government that is inclined to decrease FDIC rather than increase, you might end up not really getting much value out of that cash.
250k is not a very big nest egg for retirement.
I use far far less if I use a very small amount twice rather than a lot once. The shampoo will mix with oils in your hair and when you wash once you just keep rubbing the oil and detergent mix back onto yourself. Using a small amount and rinsing it off will make it function far better.