"In our new system, the borehole and pump can supply full pressure almost instantly so our installer suggested we didn't need a pressure tank."

From everyone I've talked to in the well industry this was bad advice.

The reason you have a pressure tank is to keep your well pump from running on/off each time you run the water in the house. This is what kills the pumps going on/off repeatedly and why they suggest to size your pressure tank accordingly (don't get to small of a one or it will still do it). With a pressure tank the well then might run once a day or two times a day depending on the size and number of people in the house.

I`m pretty sure this holds true for all electronic devices, especially motors... running for long periods of time is normally fine but going on and off throughout the day can kill them much quicker.

Maybe you guys have a special pump? I'd call around and investigate this though to be 10000000% sure because you don't want that baby to die on ya when you need it most

Also, you guys could add a hand pump since your well under 200ft

Let me know what they say if you call around.