Shared mail box and mailbox polling frequency

I have setup a few shared VM boxes on my system. It seems to be working fine. I setup mailbox polling so the MWI light will come on each phone when a VM is left. I did not change the polling frequency from the default of 30 seconds. The users are saying that it takes too long for the VM light to go out when they delete a message. I was wondering what the ramifications of decreasing the polling frequency would be? Can I cut it in half or even set it to 10 seconds?

I changed mine to 15 seconds without ramifications, but I run mine in a SOHO environment.