Ever? If you're North American or European and use Bitcoin for more than 50% of your expenses (be that paying fiat credit cards, bills, or straight BTC purchases), I feel like keeping track of your cost base and profit/loss relative to your national currency is ridiculous.

I'm guessing the answer is never. I mean, even now if I were to own a bunch of Euros for a year and sell into dollars, I think I'd need to calculate the capital gain/loss on that, right?