I never queued more than 1 item per factory. Built up the probes/harvesters 1 at a time last night. Sometime in there I started up a shipyard building. Got on this morning, was at 12 out of 10 objects. I was then still able to queue up 2 more oupost ships (when already over), then 2 more harvesters to harvest the new planets (before actually setting up the outposts, so I still had the outpost ships as well).