'An inflated time estimate' - well there's your problem. If it's a point estimate, as it should be, it's quite easy to do. Your 'real' velocity may be 10 points, but your planned velocity is 7. That not only gives you a little buffer in the event of something unexpected (so you're less likely to miss a sprint commitment due to things your team controls), but in the event nothing takes that time, it's free time to work on what feels important.