A couple of things to keep in mind about revolving utilization and closing accounts:
1. While the lower the revolving utilization percentage the better, it's actually better to have a very small balance (1% or so of the total limits) than zero. So it's possible to go from a very low percentage to zero percent and see a slight drop in score.
2. Closing an account will not cause it to be excluded from calculations that look at length of credit history or have any kind of immediate negative impact to your length of credit history. As long as an account appears on the credit report - whether open or closed - you continue to get the full benefit of it's length of credit history. The only downside to closing an account, in terms of length of credit history calculations, is that closing an account will cause the account to be removed from your credit report sooner (typically 10 years from closing date) than if you leave it open, which then could negatively affect your length of credit history when it comes off of your report years down the road.