I did this for a while:
  1. Pay for everything on credit card
  2. Pay off balance with monthly salary
  3. Convert surplus into BTC
However there were still many instances where I needed to sell BTC to cover larger expenses. This can be expensive due to transaction and trading fees.
As of now I essentually have a 3-month emergency fund in cash, with almost everything else in cold storage BTC. But the opportunity cost of that not sitting in BTC eats away at me.
Having readily accessible cash (rather than BtC) is so important and 3-month is a good amount. The tax implications around selling BTC (as mentioned in the OP) are pretty debilitating and outweigh any opportunity cost fears.
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I think that depends on the tax system. We have a bad CGT deal in the UK, but it only applies if the BTC has appreciated in value and outperformed cash.
I think the real killer is if the price crabs for a couple years, but you're flip-flopping between exchanges and taking a ~1% haircut with each transaction.
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