I have one of the earliest z3100 machines, and I chose to get the extended warranty because I had read that the belt was likely to begin decaying after 3-4 years, and that changing it was a pain.
I was glad I did---indeed the belt began to decay and drop pieces on prints after about 3.5 years, and in addition, the power supply went. Then the carriage needed replacing.
I'd say I got my money's worth out of the warranty
I now have an essentially rebuilt machine.
David V. Ward, Ph. D.
www.dvward.comDavid V. Ward Fine Art Photography