unfortunately, most of the "old" students only comes 1-2 times a week while I come to almost every class (6 classes a week). so in most of the classes, we almost always get overwhelmed because the new students to old students ratio is about 4-5 : 1
I'm perfectly ready and willing to give back to my Kohai, but it doesn't mean that I have to spend every night just to give to everyone and getting nothing for myself, right?
Ok questions based on this.
1) Are all of the 5-6 classes a week your dojo has open to everyone or are classes classified as beginner, advanced only, intermediate etc?
2) how many of those classes each week are you actually leading/instructing?
If your classes are all open to all levels you might talk to your sensei about making some of the classes advanced only so that your higher level students can focus on more than just basics. I agree it is not fair to expect your senior students to shepherd beginners every single class. But is this really the case in your dojo or are you just not looking for ways and opportunities to continue your own advancement while also helping those behind you?
If you are teaching all of the classes every week or a larger number than what you would like then you need to learn how to set some limits. You can tell your teacher that you can only teach a certain number of classes per week.
If you are in a mixed level class and are not leading you can allow the beginners to train with one another once they have had a few classes and grab someone more advanced for part of the class. I do this myself. So far no one has died. Beginners need to learn that they are not going to be led by the hand forever. Yes the first 5-6 classes maybe they need to be taken under wing more but they need to learn to work with everyone and that includes people at their own level or even newer if someone new turns up for class that day. You are not doing them any favors by babying them.
My dojo is quite small. We only have 5 classes a week and three of those are mixed level Beginner oriented classes. But we do have two classes where we can get into deeper and more energetic training as well. Sure I miss having 5 classes a week of training that is geared for intermediate/advanced levels but OTOH I think I have really learned a lot from working with all of the new people. Even if I do have an awfully hard time not flattening them by accident.