(22 Jul 2014, 6:26 pm)Roland Pratt wrote Y reg is only between a day and a year older than 51 reg so can't see there being a 'good number of years' difference in their withdrawals.
Dates I've got are as followed:
7436-44 - new August 2001
7484-94 - all are listed as new in 2002 (7484-89 obviously registered before 28th February 2002 while 7490-4 registered after 1st March 2002).
So maximum of 5/6 months between 7436-44 and 7484-9, while there's a minimum of 7-12 months between 7436-44 and 7490-4. Plus take into account they have had money spent on refurbishment, the B7TLs will, at least, last until 2016/17. Considering 7459-64 are schedule for replacement as soon as possible and they arrived in 2011, should likely last 3 years minimum.