I don't want to get off topic but i agree with Hill on this one. If your intensions are to lessen channel utilization I would reconsider not moving the beacon rate. Clients have a habit of doing some crazy things when you start to play with the beacon interval. Just my 2 pennys.
If your concern is channel utilization. You may know already that a number of things play into 'channel utilization'.
High density of access points on channel or co- channel.
Example- excessive access points on the same channel that contribute to interference, beacons, probe responses and probe request. All of which takes up medium.
Excessive use of SSIDs
if you broadcast for example 10 SSIDS you increase your management over head as above - broadcast, probe responses, and request. I did a study and found that by adding a single SSID you could increase over head by 3-7% (w/ 1Mb frames)
Low data rates enabled (1/2 mb)
By standard your managment frames (broadcast) are transmitted on the lowest basic PHY rate. If you enable 1/2Mb frames you are allowing these to go out in a very slow manner. Disabling 1/2 rates you can improve utilization significantly. In most you can see utilzation at 40-50% with no traffic be lowered to 5%.
High TX power is always a big problem. If your APs are at 100mW. They are far extending and could be adding to other same channel APs utilization. So those beacons are going further and clients are responding to them .. smaller cells are better ...