Hi Smoozesailing,
30 minutes seems about right as the minimum time for a B777, I imagine similar to the A330. That's all well and good if there are no snags, but when several Deferred Defects, associated MEL restrictions, flying with a new trainee etc. get in the way at least 45 minutes or more is needed. Not much room for error in 30 minutes.
Regards,
Old Smokey