If your rabbits are getting on fine then it is completely ok to let a session continue. Some rabbits need more time while others fall in love at first sight. Mine personally became a little antsy so my sessions went for about 15-20 mins about 2-3 times a day until they were behaved enough to play in the bunny room. I found that feeding them together helped dramatically because they both could feel at ease with each other while eating their favorite veggies, fruits, pellets