Welcome to the Uphill Athlete forum.
Looks like you have an amazing trip coming up in 2022.
How bad would it be to extend the longest Hike/Run days from 2-3 hours up to like 5-7 hours (the time required to complete most of the hikes in my area with 3,000 – 4,000 feet of gain)?
The 24 week plan provides a good framework for your training. You will have to adjust the training volume as per your fitness level/training background. If this is the first time you are going through a structured training plan, then start conservative. See how your recover after a week of training that includes a long hike. Gradually increase volume and monitor your recovery.
Look ahead in your training plan and see the volume that is planned in Transition/Base/Sport-Specific period. Continuity, gradualness and modulation is key to successful training. As you make changes, make sure you follow these basic principles of training. Hope this is helpful.
Wish you the very best!