We are trying to study chamber music. How often and how long would you practise together as a quartet in one week? We are not sure about the relation practise time in quartet and by yourself...
Good question. When we started out we rehearsed whenever we thought we should and whenever we needed it. We were working on basic skills and pieces, so we needed a lot. We wanted to give every chord the time it needed to tune, we wanted everything to be together, sync vibrato, articulation, discuss, make plans. In practice we practiced almost every day. Now it's much less. But still several times a week whenever we need. For example, we would study almost every morning together working on our 4tet chops (and at the same time working on your personal skills: do not forget this!) and the rest of the day is yours. This becomes easier after the first year of course, when you have less other courses.
Our rehearsals have almost always been 4 hours. Sometimes we did rehearsal weekends and just rehearsed all day. But 4 hours in general seems to be a good guideline.
It also depends on whatever you want with your chamber music group. What level do you want to reach, what do you want to do. You should talk about this and draw conclusions if there are differences in the group. Which can be hard. But remember: it will be your work. It is not an orchestra that you join, with their own rules. You guys are the boss, you make your own rules, and you break them when you need to. Be flexible, kind, and draw lines for yourself. Make good appointments about what you are going to do, who does what... etc.