mira sport shower burnout

Our mira sport shower has stopped heating. It seems to have burnt out, This is the second one that this has happened to. It is fitted to the mains cold water and all electrics are new and properly fitted yet we have just lost our second shower. We fitted the same sort again so we could as amateurs do it ourselves. Would it be better to get a different type of shower or try again with mira as the new version seems to have a cut out switch. Any help or suggestions please
nipsy

How long are they lasting for?

What settings are you running them at?

When you say Burned out? explain a little more pls...

Is the water pressure good? is it direct feed or from a tank?

The shower just runs cold so assume the heaters gone. We have it on at about half way round and the mains pressure is ok. It seems to go when weve had shower on tooo hot. Each shower lasted about a year. is there a fuse though it does light up and reset button?nipsy