You can. Here's their address: teamcharlie [at] mbta.com
I wrote them about my question from a few days ago:
Team Charlie,Team Charlie Responds:
My Charlie Ticket has an expiration date of 2008 yet I read in the
Globe that I need to use it up by the end of the month.
Is that true?
Mr. Garfield:Thank you Team Charlie!
Every CharlieTicket expires 18 months from the date of purchase. Your CharlieTicket will work well after January.