Voice Acting

[Xss]

or actually singing everyday just for fun. Singing will help you increase your vocalcords' capability.

I agree. While singing won't really help for the acting part (the rhythm of a sentence, the tone and emotions one wishes to convey), it will definitely help for the rest. I have been taking singing lessons for more than a year, and while I am still a rather poor singer due to my lack of practice and overall skills with singing, many singing techniques are also used by actors, and even teachers (which I have been for the past 2 years: you want students sitting at the far end of the class to hear you without you damaging your voice in one hour! And still, sometimes my throat is on fire by the end of a one hour class). Heck, why can many actors also sing without too much problem? They've learned it in the voice acting lessons.
Not mentioning that for some works one will need some techniques: want to do a raspy voice for hours without hurting yourself? You'll have to master healthy distortion/saturation/whatever used in rock, metal, etc (Trekkie from Avenue Q anyone?).
The simple fact of talking for hours can be a challenge itself. Professional voice artists (whether they are singers, actors, dubbers, etc...) are like professional sport-persons in my opinion.
One of my life-dreams would be to master many of those techniques to be able to create many kinds of voices. Yeah, pretty useless for the everyday-dude, but well.