Enjoyed reading this Ken.
I have followed the trend/performance of a few pairs for the past 10 years & convinced a long [historical] hold say $10k in each pair set is a no-brainer, no loser.
example as seen in
https://www.stocksplithistory.com/?symbol=tqqq
https://www.stocksplithistory.com/?symbol=sqqq
Same for UPRO/SPXU, UDOW/SDOW.
The benefit that I see from playing long in these pairs is in the splits as well as after each split there are several exit opportunities of the peaks & valleys.
Take recent times taking Jan 2, 2020 a $10k play in TQQQ/SQQQ, today you'd be down a bunch, approx 15%by my calculation. So its not always +/- percentage difference = 0 or zero sum. Because each pair are at different prices, I see the long play based purely on the historical performance of the indices (DOW, NASDAQ, S&P) that an equal dollar investment in each the leveraged 3x pairs that long term is a no-loser.
except the SVXY/UVXY pairs never did work out, a loss on both sides
Folks might say 'why not simply buy & hold just the index & ride the wave', sure that works also especially adding in long ATM covered calls.
As for day/week trading the pairs I think its difficult to get in done right & timing.
Although considerable guesswork/timing when doing this in the expiring options week