Not sure if attacking mining bases is the best way, if you intend to conquer the nearby planets you're better off leaving them intact as it'll take many weeks to rebuild a mining base from scratch to the max level. Perhaps the AI reasons the same way, then again the AI is not yet fully adapted to Dark Avatar.

I seem to find a colonization phase in the AI thinking during wich he'll colonize and not build any militairy. When the phase is over, he doesn't seem to colonize anything else. Not sure how this works now with the planet colonization technologies, I tend to get them rather early. The AI also seems reluctant to research the final colonization technologies.

I'm however confident that Frogboy will get it all sorted out and that we won't be disappointed!

G-Force

Who cares, just colonise the planets yourself and sell them off.
Or do what i do... whenever i get planets i don't want (usually from surrenders), i just build markets in them, no ships and leave it to get conquored