Hi Ajmal,
One of the few links available is
http://boothco.com <link updated to site home>
This however does say that typically re-assessment is after a year. but I am aware that in where there is a contingent workforce it happens in faster cycles. Especially when feedback is on contingent/temp workforce and typically in the retail sector.
The comments are based on what we read at B-School. I dont have the text, but will ask my prof who is still there for some material on 720 Deg.
In the retail sector - I had been to an retail software and technology exhibition in birmingham on 2003 June where there were 5 vendors who were also exhibiting HR Software for the retail sector. Couple of them were also offering 720 Degree Survey Feedback. I unfortunately dont have those brochures with me. If I do come across I will share it with you. Is this something you are trying to implement or is it just an area of academic interest?
Cheers
Sankalp