When did the double combine robos started to become less of a presence? It's weird after Toradora Onitaijin and Extreme King-Ohger, they gave up with Boonboomger Robo Jet. Now Whiteburn is pretty much forgotten and replaced with Akatsuki and Ryotegasword. Looking back even further, Kiramager really killed the momentum of synergy Sentai had with the dual robot approach. No Drill Kiramajin. No Twokai ZenkaiOh. I wouldn't be surprised if they give up on the extra Robos in general and go back to the Extra hero's mech only exists to be add-on parts for the Main Robo like Dragon Cesaer and Jet Garuda.