Hi Ajmal,
One of the few links available is
http://boothco.com <link updated to site home>. This, however, does state that typically reassessment is after a year. But I am aware that in cases where there is a contingent workforce, it happens in faster cycles, especially when feedback is on the contingent/temp workforce, typically in the retail sector.
The comments are based on what we read at B-School. I don't have the text, but will ask my professor who is still there for some material on 720 Degree.
In the retail sector - I had been to a retail software and technology exhibition in Birmingham in June 2003, where there were 5 vendors who were also exhibiting HR Software for the retail sector. A couple of them were also offering 720 Degree Survey Feedback. Unfortunately, I don't have those brochures with me. If I do come across them, I will share them with you. Is this something you are trying to implement or is it just an area of academic interest?
Cheers,
Sankalp