10 years I believe. Within which time, when we get promoted to the Premiership, we get several hundred pounds in return for supporting the club financially in their hour of need.
Just found an old programme from 2005 Pay £150 & get £30 off your season ticket for the next 6 years. If BFC get back to the Premiership within 10 years, bond holders get a one off £300 payment. Hope this helps.