I’d recommend checking out this article to see what different ways we recommend extrending your training plan:
https://support.trainerroad.com/hc/en-us/articles/360025556952-Too-Much-Time-
In your case, rather than doing two full Base/Build/Sepcialty Plans, I would likely recommend starting with two full base plans, followed by two cycles through Build/Specialty. This would look like:
Traditional Base (8 Weeks)
Sweet Spot Base (12 Weeks)
Build (8 Weeks)
Specialty (8 Weeks)
Build (8 Weeks)
Specialty (8 Weeks)
If you’d like, you can choose to focus on a different aspect of your training during each Build/Specialty cycle, ideally increasing in specificity as you grow closer to your event.
I’d recommend checking out this article to help you select which Build & Specialty plans to choose:
Cheers, and good luck with your training!