First of all, I think you should point the reasons to change your machine. If it is working properly I see no reason to do it, but that's me.
One very valid reason would be to build it yourself and learn in the process, but to me, having a working printer gives you a lot of freedom to build other printers, so I'd rather keep the Printrbot and build a new one.
Worst case transforming the Printrbot to a Tantillus would be burning something out due to bad wiring, so you would be risking your actual machine.