Spirits red/green and drop to zero has been explained here ad nauseaum.. Some on here are just too dense or ignorant to understand it. Thank goodness this JCBA will be hashed out by more than a few einsteins on the interweb...

I bid 70% in base in the right seat. Every month I am able to drop the trips I don't want to fly (sometimes all of them) and list for x/y or pick up quality, straight time trips on days that I choose to work. The ability to drop all the way down to "0" and build back up is invaluable.