To me, the term "profit taking" is only meaningful when you invest in individual stocks, and have had a huge run up. Kind of like this poster, when he said he watched a $50K investment ballooning up to $600K, then crashing down to 0. See this
When you are investing in MFs, you are only rebalancing, or in the extreme case, market timing.
I have never had a stock that went up 12 times like the above poster to know what I would do, although I have had stocks that ran up 2X, or even 4X. Additionally, I am so conservative that the single stocks I would put $50K in are established companies that would never go up that much.
About taking profit, I remember reading a book by John Neff. His claim-to-fame was as the manager of the Vanguard Windsor from 1964 to 1995, where his annualized return of 14.8% soundly trounced the S&P500.
Anyway, John Neff said one should not be too greedy. He said one should always "leave something for the next guy", and that he was never "smart enough to get out at the very top". He said he'd rather sell too soon than too late.