As I have had many messages asking if there are more tracks to listen too, there is currently a great three track sampler at the Silverfall website which can be found here http://www.silverfall.info/?cat=18
Hi Mikey it would appear you can add longer play times but how I do not know, as this is done through the Labels and Artists interface. The last.fm FAQ section is limited on this subject also.
Good luck with it and I will call back to check out what you have added. ;-)