As you know, Microsoft Points will gradually disappear as they are replaced trade for many months by gift cards Xbox (which you can buy from the Microsoft Store, for example). What you do not probably know is that the points you add seem to have an expiration date. A date is 1 June 2015 as you will notice here that is confirmed on the site faQ Xbox.com.
Announcing the end of Microsoft Points, the American manufacturer had announced that the "amount added to your Microsoft account will expire one year after the date of card usage and Microsoft Points codes." It seems that Microsoft wants to get rid as soon as the last card still in service. You are now warned: it'll one year, one month and ten days to settle your account.