does anyone know how long the gig is likely to last?

just got my tickets in the post this morning - and its my birthday! Hooray!

you see, it has a starting time but I'm hoping that it doesn't go on too late as the person im going with has stipulated a time to leave...I don't wanna miss the orb again, last time I saw them in 1998 (Royal Albert Hall), my ex decided to leave 30mins from the end and i was forced to go with him! Grrrrrrrrrr!