I know a couple of instructors who do them but I do not consider them necessary for myself yet. The way I see it is the higher you get through the grades the more you will start chasing masters around the country. If you started Aikido recently then private lessons are more a waste of money, you can learn things in regular classes. Although I know of a person who started learning the art and have been taking private lessons for a year, until he got his shodan. He could afford it because he owned a building company.
Anyway, this is only my opinion. If you feel that private lessons will help you more than regular classes then go for it.