How long has Locke been MIB by Lost Lin

I don't know if this has been brought up before. If it has, I apologize for repeating.

I just re watched Hearts and Minds. Not one of my favorite episodes, but that's another story.

Locke's mannerisms when testing Boone just resonated with the Locke we now see as MIB.

When Boone first tells Locke that he (Boone) doesn't want Sayid flirting with his sister, Locke says to him not to make an enemy out of Sayid. That they will need him on their side.

Then, in the jungle Locke questions Boone about wanting to tell Shannon that he and Locke have been out working on the hatch. Locke asks Boone is he sure and if he realizes the consequences. Boone insists; Locke knocks him out, ties him up, puts some hallucinogenic goop on his head and leaves him. All this time Locke is acting very much like MIB.

I also think the Shannon Boone found in the jungle was also MIB, testing Boone. She questions him thoroughly about what he did to Locke and once Boone tells her about the hatch, Smokey comes and destroys her.

In watching this episode with the knowledge of the MIB we see in season 6, I think MIB has always somehow possessed John's body. I think MIB has orchestrated situations to test the Losties since season 1.

Toward the end of the episode there's a scene between Jack and Locke that's almost identical to the opening of The Incident. Locke sitting on the beach, Jack walks up and asks if he can join him, and asks Locke has he seen any boats.