Oh my, Kiran...Now that is a very personal choice!...it is the same as having your colors in the same place so your brush just naturally goes to the right color! That is how you should keep your brushes, in a way that is handy for you
! I keep the brushes I use the most often together in a special vase (a pretty little Asian style vase, it is short, with a wide opening and a bit heavy)....when I'm working on a painting, I take out the brushes I will use for that painting and keep them on the paper toweling on which my large water jug sits. They sit there protected and ready to use....and it works for me. Keep your brushes in such a way that works
for you. What I would recommend is make sure (if you use other mediums) and you have nice sables, to keep them separate from, for instance, Gouache (which tends to wear at the brushes)....And, by keeping my favorite & used-most brushes
together, if I need a larger or smaller brush at a moments notice, I have it right there, no searching!