From my own experiense I got a 6mo to a year old male bunny Bugz and got him desexed. I also ended up with a 4 – 8 week old female, when she was about 2 months old (I had her for a few weeks) my sister put them together and they got on fine. I left them like that. i did however watch for signs of fighting, however Bugz has established himself as top dog and when Anya tried to change the pecking order he would convince her otherwise. i had no really fighting just a few hump wars. I had Anya booked in to get spayed earlier this week and the week leading up to her getting spayed i noticed a bit of agression on her side but no enough for me to warrent splitting them up. Once spayed (and is is only 2 days since) they are back together (due to Bugz braking out of his cage and into her) and there is no agression. Having said all of that in the last month there has been someone at my house pretty much 24/7 and everyone knows that if there was any agression to split them ASAP even if they think there is agression. I am LUCKY really lucky and as others have said this is not the norm. Even my vet was suprised that i had them bonded and together without fighting before Anya Spay and recommend that i keep them apart for 4 weeks after her spay and rebond however Bugz had different ideas!. It can work but is can also go wrong VERY quickly.
I have heard of others who had a bonded pair and then they spay one and the bond breaks and never re forms after spaying.