It doesn't matter how long the pump was designed to last, if a valve is closed or yo run it dry, it will be destroyed in just a few minutes. I don't really understand what you did to fix the pump case, but the impellers are probably melted as well. If the flow rate is off by that much, it probably won't build the pressure needed either. But if it is pumping any water, I would use it until it quits. That is a strange looking pump, more like a sump pmp than a well submersible. Sorry to not be of more help, but you are lucky if it will pump anything after being deadheaded like that. Also you screen name "terrylove" is the same as the owner of this forum, so we are confused as to who you are and what you are wanting.