I recently changed my wheel bearings on the S4, and everything seemed fine, but after I put about 200 miles on it, it started to sing at about a 20mph roll, the sound does not seem to be getting worse or better, will this sound likely go away or do I need to get back in there and replace it?

 

Replace it. Thats whatheppend to mine when it first started to go bad. Little ringing whistle to it then the Humming and rumbling came not to long after.

 

wheel bearings are annoying

 

I just replaced it!!!!! Do you think I could get a free one from the company I bought it from?

 

It's gone again.

Doubtful you will get a free replacement.

My guess is something was not torqued to spec, & caused to much stress on the new bearing.
Or you did get a bum bearing, make sure you use a OEM spec one!