There is certainly nothing wrong with locking in profits by "closing a winner early". Of course, the only way you know a winner was closed early is if after you closed it, it continued in the same direction. We can never truly know when a winner should be closed.
There is a psychological facet of this that you have to deal with.
For example...
1. I was letting some winners run over the past month. Some I closed to lock in profits, and they continued (by a lot). Damn it! Closed too early! I'm an idiot!
2. Some I locked in and they reversed right away (by a lot). Yay, closed right on time! I'm a market genius!
3. Some I let run and didn't lock in, and they reversed to half the full run. Damn it! Didn't close when I should have! I'm an idiot!
4. Some I didn't enter at all, and price reversed from where I would have gone in (by a lot). Yay! I'm a market direction judgement genius!
5. Some I didn't enter at all, and price went in the direction I thought it would (by a lot). Damnit! I'm an idiot.
6. Some I let run and they didn't reverse, and I got out when the run ended. Yay, market e. coyote, SUPER genius!
And so on and so on, you might be getting the point there.
And that point being, no matter what you do, you just cannot ever get MFE to exactly = profit, and MAE to = zero.
Numbers 1-3 are the easily tackled ones.
Also, there is nothing wrong with closing a winner early and then re-entering right away to let it continue on. (That hopefully will lead to number 1, and then 6.) This way you could take that earned profit and use it for something else, like pay a bill. Or, you could just let winners ride by not closing, which will invariably lead to the same results as 2, 3 or 6.
Sorry, a bit of a ramble there. AIAO or SISO, it all comes out in the wash. What is probably of paramount importance through all of this is that no matter WHAT happens, winning trade or loser, there will ALWAYS be more trades to take, always more opportunities. Don't get too wrapped up in trying to squeeze every ounce of brain food into the decision of whether to let a particular winner run or not.
Take what you can manage, and manage what you take.