[godwine]

As far as I know, you can go as many days as you feel like as long as they have classes for your belt rank.

Karate is not JUST Karate, style does make a difference. Traditional Goju and Shoto ryu already have a huge difference. I myself for example, am in Goju, its a very very different style than Shoto, and definitely different from Combat Karate. So it really depends on what your goals are

And as fro martial art that train you hard, I don't think its only limited to striking art, try Judo and tell me if it trains you hard or not

What do you want to gain from Martial Art? Like what kind of things you are looking at to learn?