Learning more than one language... at once?

This is a question I ask myself almost every time I study! I won't say how many languages I'm currently studying, but it's well over five. I'm not sure if I'm being productive or clearly just hindering myself.

My issue is not 'mixing' the languages, but rather studying to my full capability. Everyday, I have a habit of studying both Chinese and Korean at the same time without any difficulty. Although, I had to quit Japanese for now becuase of the energy it took to study three different languages, not to mention the chinese characters that were involved =-=;;;

As of right now, I haven't experienced any real problems with learning multiple languages at once. I found an interesting article that states what should be considered when learning multiple languages:

1. Goals:
If you are a casual learner who is just fascinated by cultures and or a language and have no desired time frame to achieve a certain level of proficiency then learning multiple languages simultaneously may not be too much.
However, if you would like to learn quickly then your efforts would be best spent learning one language. If you focus on one language at a time you will learn faster because all of your efforts are concentrated on one thing and not divided among many.

2. Ability:
If you are disciplined and have strong study habits then tackling two languages at once may not be difficult for you. If you are easily distracted then it would be in your best interest to learn the language enjoy most and then to come back for the second.

Article Source: http://EzineArticles.com/386107

In the end, I think it depends on the person's abilities and habits.