This study shows the results of owning USAC since it’s inception in 2013 compared with holding three other assets. The concept of holding an MLP until obtaining a step-up in basis and avoiding all accumulated taxes at that time, is often touted as a wise investment strategy. The one point never mentioned is that any other asset would receive the same step up. The 150K in tax free dividends received over 12 years is admirable, but you are forgoing the much larger tax free gain in principle you would have received by investing in QQQ, IWY, or SPY.
I can envision a strategy where you reinvest 1/2 or all your USAC dividends and create more growth (in shares & dividends). The growth would be better, but on the other hand you are limiting your flexibility in the future as the position grows. If you need to exit or reduce this position prematurely for unforeseen reasons, a large portion of the taxable gains are taxed at ordinary income rates (not capital gains rates).