How often to go to class?
Of course, part of this issue is what the individual student is seeking. Another aspect that is delicate for most is, how much commitment to make from the start e.g., to change in weekly routine, to adjusting to unexpected daily events, to practice amidst an unfamiliar process. Needless to say, getting oneself off on the right foot influences how the whole thing moves forward.
In the shorter term, particularly for more beginner students, folks tend to benefit from more support and guidance from the instructor and also unconsciously from the existing peer group. There's always some adjustment needed when "merging into" any dojo culture. Regarding how frequently one should practice, it's useful to gauge at the beginning explicitly how much commitment you want to put into it e.g., attend 3 times a week for 6 months, even considering the life events that will crop up. Commitment can become clearer as one practices. For example, you may see other students who have been there longer than you, and make up your mind you want to do a particular skill just as well as them. And in the case of aikido, some experience a sensation that is captivating or fascinating, and commit to knowing more about that experience or even just to feel it again.
Humans are not machines or robots. We are not only complex beings, more in flux and more interconnected than we usually acknowledge, we are also the cumulative conditioning the we have gone through in life until any given moment, e.g., through our family, society, media, personal values and biases. While many other activities that are available may be appropriate to apply the expectation of some kind of result within X number of sessions or weeks, a life practice like aikido may confound such a perspective.
In the long term, each student undergoes their own process. This process is slowed down or lurches forward according to each individual - their inner workings as well as their interaction with their environment. The role of the teacher is to observe and create the space, the circumstances for students to undergo their own processes. Creating the space includes nurturing a social environment in which everyone supports and respects each other and it becomes possible for people to have the opportunity to feel what they feel, work on what they are drawn to, etc. in the context of what is being presented by the teacher for the class as a whole to work on together.