How long before explosion?

[onthedownlow]

bik wrote:
Mstudio raised a good point that I forgot – the splice needs to be inside one of the boxes, NOT just hanging in the wall, so hopefully the box is where you did it.

While you should do this inside a junction box, not only because it is code, there are options that are code-approved (in most places) for splicing or extending cable runs without needing a junction to do it:

Tyco Romex splicers
http://www.homedepot.com/s/tyco%2520romex?NCNI-5

They are very easy to use, although expensive to use compared to junction boxes, so only use them when/where you need to.