onlineleben - 8:00 pm on Jul 25, 2011 (gmt 0)

Could you tell me in your opinion how long is "long duration"? Are we talking days, weeks, months?

It depends on the nature of the product you are selling. When it is easy to make a sales decison, a shorter cookie life of a day (like amazon) or a week may be sufficient. When more research by the prospect is needed, eg. in travel or education, longer cookie lifetimes (max 60 days) helps.