We are on different season cycles. GCA starts practice in July and the races are in September and October.
Does your season end soon?
One thing that you should always ask yourself with regards to training and racing is, “Am I having fun, do I enjoy this?”. I love the fact that you want to improve and are willing to put in the work in outside of the NICA practices and season to make it happen, but don’t let it go so far that you burn out or over train. You have many years to continue to develop and to become a competive cyclist, so don’t try to make it happen over night. Play the long game and it will pay off. Always make time to just have fun on the bike. You have plenty of races in your future to show how good you will become.
Other things to consider along with endurance training is improving your skills on the bike, improving your core fitness and strength in the gym, and improving your race craft. Spend time sessioning on the bike, especially cornering. Being able to flow through corners and maintain speed without having to sprint back to the group everytime will save so much energy. I actually use a coach for skills development and endurance training because as a 51-year old, I came into the sport late and my road skills and fitness didn’t translate to the dirt, and I ended up on the ground way too often. My coach currently coaches a young GCA cyclist that is an absolute monster on the road, but struggles to break the top 10 in GCA MTB races. It isn’t because he doesn’t have enough fitness or power, it is because over the course of the race he is sprinting out of 100s of corners to stay with the lead riders. By the 1.5 hour mark he just can’t continue that level of work to hold onto them. He will be a different rider this year after spending the past off season sessioning and working on bike skills. You are probably already a very skilled rider, but we can all get better.
Best of luck to you. I hope the rest of your season goes well.