Under My.Maxon.net - Assigned Licenses and Available Licenses will show different dates for the same license. These dates convey different information.
The Valid Until date under your Assigned Licenses will show when your device needs to be online to sync your license. This date shifts every 14 days. For the most part, you can disregard this date unless you are often working in an offline environment. This is not when your license expires or renews.
The Valid Until date under your Available Licenses shows the actual end date of your license. You can refer to this date for information about when your license will expire or renew. Whether or not this date means expiration or renewal is dependent on if you have auto-renew enabled on your subscription.