Part of the E3 stuff included Microsoft moving away from their points system and moving towards local currency. FAQ on it is up and interesting.
When the Fall 2013 dashboard update hits, all remaining MSP will be converted to local currency.
The money that was transferred/converted/whatever will expire in 1 year from the date it changes.
So yea. looks like I have nearly $40 to use up this summer.
http://support.xbox.com/en-US/billing-a ... retire-faq