Extend text effect

Hi,

I had a black background with a "fade on" text effect applied, when I noticed it was too short to be read, so I dragged my bg with the right arrow (placing my mouse pointer over the right edge of it) and extended it for a couple seconds; then I did the same thing with the fade on effects but instead of getting a longer whole effect, it got split in 2 parts, like fade to the first part of my bg, then fade again to the extended part of my bg.

So how do I do this without cutting the whole effect and adding it back?

Thanks