A plumber recently turned down our cylinder thermostat to 60C, saying the high temperature could generate bubbles and damage our shower pump. Since then our showers are less powerful and the shower stats have to be set way above the safety stop to get a reasonably hot shower. We probably hadn't touched the cylinder stat for 15 years before that, so it was not generating obvious problems.
I am concerned more about the quality of the showers (thermostatic mixer showers running off a pumped gravity supply) and having adequate hot water in the cylinder than economy, though not wanting to burn money unnecessarily. There are no children or vulnerable adults in the household likely to scald themselves.