When I incorporate weights, I try to live by two principles: Power or conditioning. You start getting in bodybuilding rep range you'll feel the fatigue when you roll, but especially when you work standup. Also, the pump you get from lifitng isn't necessarily inductive to success in an actual fight, if anything it can be debilitating. That, and injury prevention is why you hear of fighters working more cardio and strictly skill training the closer the fight gets, along with plenty of prehabilitative work. I second JudoJosh, you can't reproduce the kind of conditioning you get from actually rolling/sparring or the way you can functionalize and capitalize on the strength you get from the gym. I know plenty of guys that can toss iron around all day and make me look silly with weights but when we start rolling I feel like I'm twice their size.