I'd be interested in the logistics behind a 2,500-foot rappel. Assuming you are using 7/16 or 1/2 inch rope, this would be an awful heavy batch of rope! I've lugged 600-foot bags and they weight about 20-25 lbs, including the bag itself. Also, the weight of 2,500 feet of rope below you might be so much so as to effectively act as a bottom-belay; i.e. depending on your rap device, it may stop you before you get started (what type of rap device are you using?). On a figure-8, it could be a problem. Maybe not so on a brake bar.
I know two people (cavers) who rappeled down to the bottom of a vertical 5,000-foot mine shaft in AZ. However, they did a series of rappels and had the extra bonus of having to ascend mechanically out of the shaft.