There were three to four classes per day at Hombu for most of the Aikido seniors out there. Class time was an hour to an hour and a half? Don't have my notes here.
But, from around 1945-1955, classes at Hombu were uncommon and not well attended. And during those years, Ueshiba Morihei didn't spend a whole lot of time at Hombu. If he did, it was lecturing most of an hour for one class (the early class).
Even from 1955 to his death, Ueshiba Morihei really only had one official class (that is when he was at Hombu and did actively teach) and that was the early morning one.
I just want to clear up something... since there is a revisionist tendency prevalent these days that the ushi deshi didn't really spend a loot of time with the Founder. Yes, the Founder only taught his early morning class daily. But the ushi deshi were with him every moment of every day. Training was a 24 hour a day issue for them. Chiba Sensei talks about the job they had of helping O-Sensei to the bathroom in the middle of he night. He learned to come awake just as O-Sensei opened his eys and was ready with his slippers. That's training.
Saotome Sensei has talked about the fact that they went everywhere with the Founder. When he went to Iwama, he had deshi from Hombu with him. He would show them things on the train, they would do all the misogi he did, they would get pulled out of bed in the middle of the night and shown stuff O-Sensei was thinking about. That was training.
O-Sensei was open to questions as well. Saotome Sensei used to ask him questions all the time. I gather he was something of a pest... And he said O-Sensei would always show him something when asked. He wouldn't explain, if you got it, you got it, if not, look more closely next time.
It is clear to me that, for the post war deshi, more of their training from the Founder himself was off the mat rather than in formal class, although they had that daily. Not only did they have class with him daily but they took all the ukemi. They had their hands on him to feel it repeatedly every day. Then they spent many hours a day assisting him, traveling with him, listening to him, absorbing more from him than they could possibly absorb at the time. Most have spent their lives digesting what they got during that period.
This tendency towards saying that these guys were really students of Kisshomaru and Tohei and not really influenced very directly by the Founder is a set of theories putout by people who either, a) haven't talked to many of these teachers who were deshi at the time or b) who have a particular point of view favoring another interpretation (like the Iwama folks for whom Saito was clearly the guy who had spent the most time with O-Sensei). This viewpoint is hard to credit once you talk to the actual people who were the uchi deshi at the time. Now some of them, like Imaizumi Sensei, did consider themselves to be students of other teachers, like Tohei, once the Founder had passed. Saotome Sensei definetly considered Kisshomaru as his teacher, once O-Sensei passed away. But every aspect of Saotome Sensei's Aikido was and is informed by his experience, on and off the mat with the Founder.
So I take this revisionist thing with a huge grain of salt... I've talked extensively with folks who were these deshi and know how deeply they were effected by the Founder, technically, spiritually, etc.