Personally, I don't mind if you pick up an email thread months or even years later. It happens ALL THE TIME in archives. Sometimes you think you're ready to tackle something, but you find out (surprise!) it's way bigger & more complex & emotionally loaded than you originally thought. That's okay!
Oh, and also: we need to normalize shame jubilees. We should hit the point where someone sends you an five month old email and they're like, "Hey, I'm finally responding because I'm on my shame jubilee" and you're like "Oh, that's awesome, I'm so glad you're having one right now!"