Peter Lynch is pretty famous for taking Fidelity Magellan (FMAGX) to heights and his books talks about his strategies and how he handled the 1987 crash. He took over when it was a small fund and it became massive. I presume when he stepped down, Fidelity considered his replacement very carefully.
Magellan continued to outperform for a while. In 1996, one of the managers tried to outsmart the overvalued markets by investing heavily in bonds and got creamed because they called the top too early. It essentially became an index tracker after that and underperformed after the financial crisis.
This is an anecdote at best, but it is one that illustrates manager risk and the difficulty of continuing that performance as a large fund.
I was invested in FLPSX as one of the less-bad options in my 401K and familiarity with Fidelity, and it was essentially a mid-cap index tracker. It looked nice compared to the S&P during the 2000s but I could have easily bought a mid-cap index (except at the time, I really couldn't do so).
Logistically, if I were to try successful investment managers, I am not sure how many years are enough to prove outperformance and, once established, how many years they have left at the same commitment level. In some ways it might be harder to bet on individuals rather than betting on companies, if I had to choose.
People should invest how they are comfortable, but looking at very long term performance of a ticker might be useless simply due to employee turnover and I would caution people who asked my opinion.