The 90-day fight is the inevitable conflict that occurs approximately 3 months into a romantic relationship. The relationship will go "perfect" until just before the fight, when the female will begin to show minor signs of dissatisfaction and escalate it into a fight over a period of days or a week. A blue pilled man will generally be caught off-guard and seek to be conciliatory about whatever the cause of dissatisfaction is.
A more effective method, usable only by a red pill man, is to look out for minor signs of dissatisfaction or indicators of disinterest (like suddenly taking longer to answer texts, but CERTAINLY before she does something as unthinkable as public disrespect), and then seize the initiative by starting the fight himself just before she has a chance to escalate by seeking out a fault and throwing it at her. This method is particularly effective is he makes a real threat of leaving her. (I don't recommend bluffing, but putting yourself in an advantageous position so that you don't have to.)
The faster the fight is brought to her, the more shocked, off-guard, and put on the defensive she will be. The fight can be brought to a conclusion once she becomes conciliatory.
This works whether or not you want an LTR. It's more effective for an LTR because it sets the tone for a lifetime.
I have occasionally tried to warn men when they get into the early stages of what appears to be an LTR. They always blow me off because it seems like they've found "the One." They're fucking every day and they can't see why it will ever change. But I've never been wrong. It always comes, and it's always right around 3 months.
Fuck them. I don't ever bring it up any more.