There are two checks you can easily do on your coolant: whether you have enough of it and if it’s still protecting your engine in cold temperatures.

Faster is not better when it comes to engine coolant flow rate. The purpose of a radiator is to support heat transfer, which is a time-dependent process.

Lowering the eco-mode to about 55-60C on your condensing boiler will turn down the radiator flow temperature, which dictates the temperature of the water that travels through your radiators.