I see your point. I thought you were speaking of the long-term; not just a few months in duration.
I expect that from a pure buy-and-hold aspect then the point at which the returns merge and coincide are strictly a matter of data mining which starting and ending dates one wants to use to determine that.
I have now owned three of the ultra ETFs for several months. I am pleased with the results. My purpose in purchasing them was not to buy-and-hold per-se, but to obtain more AIM directed transactions because of their increased volatility than I would have obtained from normal mutual funds. Someone once remarked that if one wanted a good mutual fund suited to AIM then the mutual fund should be rated an "A" in a bull market and rated as an "E" or "F" in a bear market. The ultra funds seem to have those traits. I think Mr. Lichello referred to this trait in his book as being "juice".
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