I attended my first seminar two months after starting aikido, and have thoroughly enjoyed everyone since. I try to attend at least three a year. I find them to be an excellent way to broaden my knowledge and training. I always come away from each seminar with at least one or two new insights or understandings about aikido. Plus, it is just so cool and so much fun to be with a huge group of people all practicing aikido. As far as the intensity level, I've found that you can take the practice at whatever pace suits you.