Here is my thought on Buy & Hold vs. Buy & Sell (flipping)

buy & sell is actually Flipping. During boom period, you may not want to buy and hold because prices are rising very fast. As a committed buy and hold investor, you SHOULD HAVE ALREADY finished your buy and hold moves during PRE-BOOM period. Which is from right now to early 2010s. By the start of next boom, flipping (Buy & Sell) is actually the best short term strategy.

To be more clear, Buy and Hold should be the fundamental approach, all your flipping approach should be laid on this foundation. Buy and sell (flipping) can be and should be used to supercharge the foundation.