you can find more details about the available Skype call recorders by visiting the link below. Basically, the length of call you can record may depend on the brand and version of the Skype recorder you will be using. For most full versions of Skype recorders, they offer recording time almost with no limits.
if you want to see specific instructions, you can also check this entry in my blog -http://skypefordummies.blogspot.com/2011/05/how-to
you can use supertintin as this one has no recording time limit. for more details, you can check it's page in the Skype Apps Directory section;