That is fair enough in most cases however some sites out there are no longer maintained but still hold great information, such as
SmallandFurries.co.uk. And as you say it can sometimes take ages for them to reciprocate the link as generally people want to check out the content of what they are linking to which is perfectly understandable.
It doesn't hurt to ask though and everyone is therefore encouraged to contact the owner of the website to see if they would be interested in putting up a link to Hamster Central - make sure to give them
http://www.hamstercentral.com
as the webaddress to link to, not the forum address