I couldn't find anything in the rulebook about whether cards and resources taken from the planet are replenished in the next round or are a one time prize. I did find it odd that the rules said you don't have to take everything. Why wouldn't you?
You claim then every round. The reason you might not, is because if you are low on cards you might lose by drawing all of your cards. Rare but possible I guess. Also some cards/abilities may allow you to do something only if you have less resources or cards than your opponent and