Formula to Calculate FIFO VS LIFO for Financial Instruments

Assuming that this is the U.S. ...

Short term trading is not part of this equation. You're in, you're out and gains are taxed at the same rate as your ordinary income. FIFO, LIFO or averaging don't apply.

For your investments, share cost basis per tax lot may be sequentially higher or they might be zig zagging up and down if you were building a position over time. That means that earlier positions may have cost more or less per share. So some data sets might benefit from LIFO and while others from FIFO, or not at all.

If not salaried, your tax rate may vary from year to year. That would mean that in lower income years, you should realize larger gains and in higher income years, lower gains. That suggests lot designation over FIFO/LIFO.

I think that there are too many variables in play. The only way to know what the best plan of action and result would be would be in hindsight. So my gut feeling conclusion is that you should just sell the lots that best fit the circumstances of each tax year.