When and how do I put my cockatiels to sleep in the same cage at night ?

[Rosalindagg]

I got Tito in January and so far him and Sushi have been sleeping in separate cages. When should I start sleeping them in the same cage ? Is there some steps I should take ? They get along and haven’t fought just the occasion peck when they’re aiming for the same toy or same piece of food. I guess I’ve been scared to sleep them together in case they fight at night. They’re both cockatiels. Not sure if that has anything to do with it. I’ve done it with my budgies and it was super easy but Sushi gets feisty when she can’t see so I think that’s why I’m a little scared.