When you log in to the Astronomy in your Hands web site, your log-in is recorded as a cookie. Obviously you cannot log in at all if your browser does not accept cookies. (Find out how to enable cookies here. Find out what cookies are and how they work here.)
The log-in cookie is set to expire well in the future in effect it will never expire. However, if the cookie is deleted or modified by maintenance or upgrade activities to your computer, it will be necessary to log in again.
If you have a group or site license you are entitled to log in as many computers as are covered by the license. This can be done by logging in each computer individually using Subscriber Services and entering the license number. Propagating the log-in across a network is easiest with an Auto Login page.
Note that you may not log in any computer that is not covered by the terms of the license you have purchased; see Copyright and License Information.