The licence on your existing transponder is valid for 12 months. This is the page on the mylaps site that tells you how to renew and activate the Pro Chip Flex transponder license – http://www.mylaps.com/en/how_to_renew_FLEX
And this is the renewal page for the Pro Chip Flex transponders we use, they have several options from 25 Euro for 1 year to 89 Euro for 5 years !! http://www.mylaps.com/en/products/prochip-flex-subscriptions/629
Once you have renewed the licence you MUST use the license manager software, to activate the new license, just as you did when you first purchased the transponder.