Actually, for me it is fairly different. I live overseas so I do not pay income tax up to my first $100k of income. I live in Germany where Capital gains on bitcoins is zero after a year. So I can buy and hold all year with these coins and spend my other coins. Simple enough to keep track of with one address for income. I can just change addresses in a year and start spending this income.
If you are a U.S. citizen, you must pay capital gains at the U.S. rate.
Yes, as long as I follow the same process of FIFO or LIFO. I think LIFO makes it easier for keeping close to the price I paid when I spend.