got my NIS for Mac through Comcast but it has a subscription expiration date?

I am a Comcast Cable Internet subscriber and they recently switched to Norton from McAfee as their security software included with your paid monthly service to them.  They have both the Norton Security Suite for Windows and Norton Internet Security for Mac of course I downlaoded the Mac version there is no way to tell if this is dual protection or just the regular NIS but I notice when I check my stats it says expires APR 13, 2011.  When I've used both McAfee and Norton products provided through ISP's on the Windows side the area that normally displays subscription  status xxx days remaining is usually not there and you get continuous protection as long as you are a customer or until they switch to someone else.  What will happen when I reach the expiration date and try to renew?  I'm afraid of  accidently being charged for a new subscription if I renew it.