That's a good point. A fuse, properly selected, would blow and protect the pump, to some extent.
Otherwise, the idea of 120V AC crossing into the DC circuitry is a little far fetched: you can just be careful.
As for the wear on the pump, most of them don't have any friction that is significant to warrant turning it off, but the high temperature that some pumps may reach, could be a concern. Then again, those temp cycles (on/off) are a source of wear themselves.:shrug:
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