I've used them. They worked for me but I got real bad sus flu on them at first. Apparently the Karachi stuff is more prone to this as it isn't prepared in perfectly hygenic conditions but it is legit.
About 5 days. It is fairly common with sus and there are many posts if you look up 'sus +flu' but particularly common with the Karachi Organon so I have been told and experienced. After that you should be fine for the rest of your course. Take plenty of water and vit C and multi vit before you use it and during to help raise your immune system and lessen the effects of the flu.