One of the things I learned very, very quickly as a techie was to avoid giving an estimate of how long as job was going to take at all costs, because someone, somewhere would treat your word as a cast iron guarantee of job completion
Aircraft maintenance is not always an exact science, and with the number of systems that this aircraft has, and their age and complexity, the team must have been faced with a daunting task in restoring her to flying condition.
In her day this old lady would have been maintained by a mass of experienced techies with spares on demand, full sets of APs, manufacturer support, and of course she wouldn't have been laid up for years doing nothing, gathering dust, moisture and corrosion in her vital parts. The team are having to re-learn old systems and also train up people who have never seen a Vulcan fly in their lives. I am actually amazed that they've got this close, and always thought that the estimate for flying her this year was optimistic, especially when I saw the state she was in last year. Missed deadlines are part and parcel of the job of getting her up again, keep the faith as I'm sure they'll do it.