1) See Doggy's Post.
2) After X years, the planet will be converted to an atmosphere that the
majority of the population can breathe. So, no matter who's on the planet, they get the proper atmosphere. (As long as its not vaccuum breathers on a gas giant - you can't remove the atmosphere of a gas giant

)
If you have 60%/40% population, the atmosphere will become whatever the 60% majority breathes. If they breathe different stuff, one of the races will have to leave, or the planet will always be domed.
3) Well, if your planet gets damaged, and the conditions are deadly, you may want to fix them so your people can grow. That's where you use the CI plant.
Also, if you take -50% to environment resist, you still get full reproduction on a "Optimal" world, so you can use the plants to get full reproduction while saving racial points.
4) Repairing stuff is free. Retro and rebuilding lost ships will cost you. Therefore, repair everything.
NOTE: You can repair ships that are mothballed, so if your ship has taken 98% damage (4/105 components), then mothball so you pay no maintenance while the ship gets repaired over the next 1.5 years. You will save the cost of rebuilding a new ship, and not pay a cent while the repairs happen

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[This message has been edited by suicide_junkie (edited 25 April 2001).]
[This message has been edited by suicide_junkie (edited 25 April 2001).]