Yes, the sand and clay will wear away at the pump over time so maybe the wet end will wear out before the motor does. If the pump is as old as the house, its motor may already be on borrowed time depending on factors unknown to us. As the wet end of the pump wears, it will gradually produce fewer GPM and less pressure. I would budget for a replacement soon.
With a low producing well, if the well bore is used as storage and the level pumped down considerably, it can exert significant pressure differential between the aquifer and the inside of the casing. If you use less water, the level should draw down less with less pressure differential drawing in as much sediment at least in theory. A large pressure tank represents a significant load on the well as the pump runs full-out from the point it kicks in up to the point that the tank fill to kick-out. That means that despite using less water, the pump can still draw down the level considerably on each cycle depending on the size of the bore hole.
One approach to consider is a smaller tank combined with a Cycle Stop Valve. The CSV will meter the flow from the pump and stop the feast-or-famine cycle of the large tank.
Another approach is to slowly pump into a large non-pressurized tank and then have a second pump draw from the tank. Of course this is a significant undertaking.