I feel like I'm in the same position as you. $15.00 to some people isn't much, but when I'm leasing, I feel like literally every dollar counts. I would try and go for the 12k miles for free, but that's just my opinion. I've had horrible experiences with salesman, and have the general thought that these guys aren't my friends, and while they're acting like they are, they're doing everything in their power to screw me. I'm not saying this is a healthy train of thought (haha), but it's just how I generally feel.
Good luck with it!