You're not actually under the impression that Bitcoin value will maintain value over time, are you? If you use banks because of the "cost" of holding cash then

You're not actually under the impression that Bitcoin value will maintain value over time, are you? If you use banks because of the "cost" of holding cash then you will very well have to engage in the same type of speculation as the "cost" of holding Bitcoin. At least the bank can effectively guarantee your investment will be worth more in numerical terms over time, raw Bitcoin can guarantee no such thing.