I had to reinstall my 2010 3-User McAfee Internet Security with a 1 year subscription this month, after previously installing it on 12/27/09 and now it shows it will expire 4/19/10 instead of 12/10, what causes this early expiration date.
When you registered your software with McAfee that date should be listed in their records. You will need to contact customer support so they can update accordingly so it reflects the accurate expiration date in December.
I might point out you need to use the MCPR removal tool found under Useful Links at the top of this page when uninstalling and reinstalling your software. Once again customer service should have the information in their records as far as the December expiration date.