I hope you're joking HC
Not joking at all. We check the gauges from time to time, but we don't spend a 2 hr transit staring at the gauges. In my experience as a Simulator instructor, if you give crews a failure eg engine or transmission oil temperature rising, pressure falling etc they don't notice it until a caution light comes on. And that is with them in the Simulator expecting the worst! That is the reason why caution lights were invented! Of course it may depend on how rapidly the gauge is moving out of the normal range - if its higher or lower than normal for a long time, it might get noticed.
And as soon as workload is elevated a bit, eg flying an instrument approach, looking at the system gauges just doesn't happen.
We had a real case of an oil cooler fan failure on an AS332L some time ago, so of course transmission oil temperature rises, maybe a degree every 2 or 3 seconds, but crew did not notice until the high temperature warning light came on maybe 2 minutes later.
Its interesting to compare the diametrically opposite philosophies of SAC and EC in terms of HMI:
SAC likes to give crews as much information as possible (thus maximising the potential for misinterpretation by the crews)
EC knows that pilots are stupid and only gives them the information that they really need to know in a black and white way (or grey and red in the case of the EC225) - giving them any more will only confuse them.
On the 225, the gauges have no markings and mostly the gauge range is grey (no more Ts and Ps in the green!). The extremes of the gauge are red lines. If the gauge touches the red line, its out of limits and a caution light comes on and the numeric value of the parameter appears in yellow or red. But there is no sense of how far into the red it goes since the red line is the end of gauge travel, its either red or its not - you either have to apply the RFM procedure or you don't. You can set it to show the numeric values all the time, but that is only for those of a nervous disposition.
On the EC175 I believe the standard display will not include system gauges - they will only pop up if something goes into an amber or red range.
Being a stupid pilot, I prefer the EC way.
HC