Ah, why don't you try building up with shorter rides?
I have too many bad memories of painful early season 30-40 mile rides in March or early April, despite being very active over the winter. I know if you are training for a specific early season event, you want to ramp it up. This year, I'm not doing that. I started with 15 miles, going up to 25-30 tomorrow. I'll stay there for a couple of weeks, before progressing.

Just a thought.