We see this a lot – people are enthusiastic to get the trial started and life gets in the way. The good news is that we do have a trial extension process:
Contact Billing department at numbers listed here - http://onlinehelp.microsoft.com/windowsintune/jj839713.aspx
Step 1: Choose Option 1
Step 2: Choose Option 1 again
Step 3: Choose Option 2
As long as the current trial is still active, you can request an extension.