persistent cookie expiration

[jimfog]

Since every time a returning visitor comes to the a new cookie is created and we invalidate the old one am I right to assume that the expiration date of of the cookie can be very small-maybe even half an hour? I do not know If my logic is correct. That is why I am asking this. Thanks

[birbal]

that cookie life time should have long enough time span for recurring user (the time may be vary site to site, usually 7 days,15days even 30days). but not half an hour, it is so short time that a user can be idle. it does count as recurring user that need remember me features.