Am I missing something about how much extended actions are possible for enemy ships in space combat situation or is that some rule of thumb situation?

These are ships with thousands of crew. My thoughts are that if you pick a ship combat action, you will be able to find at least one nameless NPC who can perform it at the crews skill level.

I'm not aware of any rule limiting how many actions can be taken.

The book suggests one action for each "characteristic bonus" of the ship. So if it had Crack Crew (40), it's do 4 actions, and if it had Veteran Crew (50) it'd do 5 actions.

thnx guys. I thought something along these lines too (an action for crew bonus).