Great question. Since you have the time you are very wise to extend the base period. The bigger the base the better. I do not know your particular fitness but…….In 99% of the cases with climbers I would recommend increasing basic aerobic fitness training as the MOST important thing, beyond having the technical proficiency to handle the technical demands of your goal. You just can’t ever be aerobically too fit. There is never any downside to increasing that base. Extend the middle 8 weeks by 4 weeks to make it 12 weeks of Aerobic/Max/ ME Crossover. Do this by dropping to one Max and one easier ME workouts(as preparation) for those 4 weeks before. The ME work is the real money training that will make you a beast in the mountains. If that aerobic base is bigger in all likelihood it will support more ME and hence put you at a higher final condition. Add 2 weeks to that Final Aerobic/ME period but be cautious when using the ME workouts if you have not had experience with them before. They’re a very powerful training stimulus but a bit like playing with fire. Over do them and you WILL get burned. Make sure you can maintain a high volume of Z1-2 work during that ME period or else back off on the ME. Otherwise your condition will pop up quickly and you’ll feel like Superman then the bottom will slowly drop out from under you. You’ll wonder where Superman went. Keep that aerobic support training up during the ME period and see steady gains with it though the 6 weeks and you’ll have an additional 6 week window to use that fitness you’ve built. Yuri Verkhoshansky, the grand daddy of periodization called this the “Long Term Delayed Training Effect” I have used it with Steve and David Goettler and Ueli also practiced this method.