If you have almost a gallon of fuel on them they probably need to be changed. I've never had a set last a whole gallon.
Also look and see if when you hit the brakes, it's closing your carb some, compared to when it's just idleing. Or if when you hit the breaks your idle drops some. If it's doing that you endpoints are setup wrong for your throttle. You might need to tighten the spring up some that returns your carb back to it's idle setting whenever you let off the trottle. Mine did the same thing for awhile until someone showed me how to fix it.