I don't think you need to spend several months on base. If you did, you wouldn't be able to get to the riding season!

What would help you is to map out your 12 month training season (including 2 months for your off time). In that 10 months left, try to figure out how much will be dedicated to training, and then from there, figure out how much time you're going to spend on each training type (ie base, endurance, intervals, etc.). From there, start your training, but be aware of your progression. If you are progressing well, you can advance. But if you're having a hard time progressing, your schedule needs to be revamped to incorporate your weak points.

Try another 3 weeks of base training, then move to endurance for another 3- 4 weeks. After that, I think you'll be better ready for intervals. But now... it's just too early in anyone's training season to be looking at interval training. You'll peak way too early, and your season will cut short somewhere around early July.

Koffee