Sensei used to regularly say, "Training has to be as regular as brushing your teeth." Training like brushing your teeth has no immediate tangible benefits. It is one of those things that can't be truly measured until all your teeth fall out or when the dentist confronts you about your cavities or gum disease. Don't get me wrong, there are some aesthetic benefits to brushing like fresh breath and clean teeth but those are fleeting.
Training itself is the culmination of effort, but it too has little tangible benefit. Aesthetically you may look better, feel better or be in better shape, but those like brushing are fleeting.
So why should we regularly train if there is no immediate benefit? This is hard to answer but it is just as difficult of an argument to make as when our mothers compelled us to brush our teeth or eat our vegetables. You should do so because it is good for. In other words we should stave off pleasure for purpose. If you are too lazy to brush your teeth before going to bed then you might get cavities. If your desire is to get good at Aikido then I would advise you to commit to a regular training schedule. Basketball great Jerry West summed it up best when he commented that, "You can't get much done in life if you only work on the days when you feel good."
Training, Sensei commented, builds, "spiritual capital." That spiritual capital is what we draw upon when things get tough or we are put into a bad situation. It can be used when someone attacks you, but it can just as well be used when you have to dig deep and bury your parents or listen to a sad co-workers story. In other words, it gives you the ability to not only do the right thing but know the right thing as well.
Therefore the benefit that regular training brings is not something that is readily apparent like a large bank account or a fast car. It is something that is ephemeral like doing a good deed. You cannot save it up to a bad one because its equity is gone almost as soon as it is done. But, if you don't train, you might not be able to do the right thing at the right time, which is the mark of a good student and thus why training regularly is necessary.
Please do your best to maintain a regular practice schedule. It really does matter.