Studying two foreign languages at the same time?

Do you think it's more effective to learn/study two languages at the same time or is it better to master/concentrate on one language first and then move on to another language?

Providing that the two languages are similar(in the same language family) like Spanish and Portuguese, do you think it's better to study them together?

What if the two languages are much less in common, such as German and Japanese, would it be wiser to study them separately?

As I wrote in some other thread, I see no problem in studying two languages at the same time.

The biggest danger in studying two similar languages like Spanish and Portuguese at the same time, is you getting bored very easily.

This question has been beaten to death in every language forum on earth (and a good percentage of the non-language formus)...

You should see greg's recent post (and mine).

Which thread(post) are you talking about?