The MYW tickets, introduced Jan 2, will expire 14 days from 1st use, unless you pay for the non expiring feature. You also have 14 days from the 1st use to upgrade them to another ticket, which means if you get part way through your trip and realize you won't use the whole thing, you can pay to add the Non expiring feature. You will have to pay the non expiring amount that coincides with the amount of days your ticket originally had... so if you originally bought a 7 day base ticket and only use 4 days, you will pay the $55 upgrade to non expiring for the original seven day ticket, not the $10 fee for the 3 days you have left.
Make sense???