Having a couple of classes a week depending on your needs as a singer is good, but if you think it's not necessary, then we recommend you return to once a week. The standard frequency of classes is one class per week. Some people want to do more right from the start and others want to do less than that. For most people, I recommend consistent weekly classes as optimal if possible for them.
In my experience, people who plan to do two or more lessons a week find that they don't actually progress much faster. It takes time for the body to develop new habits, and singing is a rather sophisticated process for the body, since many things have to align. Try to take a class at least once a week. If you can have more, you'll progress faster.
If you can't, remember that practicing at home is just as important as the lessons themselves. If you work on this every day, you will improve your vocal cords and strengthen them, which, in turn, will allow you to practice for a longer time. However, in general, if you can't do 2 or 3 singing lessons a week, you may not improve your voice, even if you practice constantly at home. The only way a good singer can stop thinking about his voice and start thinking about the songs he is singing is by training his usual vocal patterns to the point where healthy vocal technique is on autopilot.