The ideal RPM range

As long as the rpm stay under the red line and high enough that the engine doesn’t buckle (aka lugging the engine) you will not hurt the engine/transmission or affect its life expectancy significantly.

The engine will most probably out live the car’s body in any case. Just drive it the way it feels right to you and don’t worry about your husbands driving habit.

I’m an automotive designer if that matters… :o)