With each of my rabbits, it was a bit different. Jack who is very food motivated got it within a few days, while Bailey was more affection motivated. It took her about a week to train ME to give her pets instead of treats when clicker training her.
Also, to keep them motivated, I learned a little trick in my clickertraining class. About every five clicks or so, give them something really special, so it keeps them wanting more. You can also use dinner time as clickertime.
During the clickertraining class I took, the rescue bunnies would learn to touch their nose to the ball within 30 minutes. With my own bunnies, they are a bit spoiled, they weren’t as excited about just boring old pellets, (that’s why dinnertime can work well for clickertraining time)
Also, you don’t want to train for too long. You should keep each training session short – each bunny is different, but when they stop becoming motivated during that session, if you don’t have any more treat tricks up your sleeve, then just let it go as they will then no longer be motivated by the clicker.