How commin is it for these sensors/sening units to fail on our trucks?

'cause my oil temp gets lower and lower as the motor warms up.... and i dont think the water temp reflects the engine's water temp... cause you touch that upper hose & its HOT.
but i figure the guage only reads...160?

and it the sensor tells the computer the temp is 160, its gonna be a little less economical on gas. cause these motors are engineered to run hot...

wish i had a point and click lazer thermometer lol! but theyre like....$300