I was wrong they do expire:
How does this change affect me?
Any Microsoft Points you had remaining in your Microsoft account have been retired and we’ve added to your Microsoft account an amount in your local currency equal to or greater than the Xbox stores value of your Microsoft Points. This value we added is promotional and will remain in your Microsoft account through June 1, 2015. However, the currency you purchase and add to your account will not expire. You can use your local currency or an Xbox gift card (denominated in your local currency), in addition to other current payment methods available in your region, to purchase your favorite content on your Xbox One or Xbox 360.
http://support.xbox.com/en-US/billing/microsoft-points/microsoft-points-retire-faq