I'm curious why you ask this question... Some thoughts of mine...
If you plan to listen on disc yourself on your own player, this should only be a technical concern for yourself. I have to think that this question has arisen because you want to spread the show in some way (privately to the opera or otherwise)...
In this situation, I think I would try to slip in an extra trackbreak resulting in a 30sec track that could be could removed, if the person cannot overburn. Crowd noise, intro, something... They can still get 99% of the show, its just got anamoly... Or they could burn the full show onto 2 discs...
If you can't do that, I would track it out for two 40min. discs. If someone wants to try and overburn themselves they can do so, but the dumbie user may not even know they could overburn...
But I think it all depends on your target audience. If it were me, and I was handing out CDRs to the opera members, I'd do a double-disc set. If I was seeding on Dime, I would seed it as a "set" and let people burn however they wanted...
Terry