How or when do you substitute your main exercise for a variation? Two cycles? Three? Wait till you stall out?
While you should stick with a lift for a minimum of a few cycles, change lifts when the ones you’re currently using no longer reflect the goals that you’re trying to achieve. I think this is pretty much up to you, though ideally stick to variations of the big 4.
What is your reasoning for changing the main lift? Injury? Weakness?
I never know who is busting my balls and who is asking a real question.
Just do the main lifts for several years. I would recommend using different reps/volume for variation as well as different supplemental work. Assistance can also be varied too. But please, don’t change the lift after 2 cycles. Or when you hit a road bump. Too many people find stalling a detriment. I find it a way to test my intelligence and perseverance.