I've been playing with Lumos - but I don't think it does what I'm asking for either.
It lets me set a custom backlight level per app - which is very nice. But it doesn't seem to override the power saving features in settings. After a couple of minutes, the backlight will still dim - regardless of the custom setting.
I think I'll keep Lumos because of it's usefulness, but it still doesn't seem to do what I want. I guess that unless someone has a different program in mind - I'll just have to continue going into settings every time I want to use certain software for extended periods of time.