How many mg per ml? I'm going to guess 250mg. I think the half life is between 16-20 days. You got 1000mg injected so just say 18 days later you have 500mg remaining, 36 days later 250mg remaining, 54 days later 125mg remaining.
I'd start a PCT between 55-65 days after last inject. Someone correct me if I'm wrong here.
Edit: He's should be about right with 3 months.