Yes. A hot water heater will heat your water to a desired temperature (adjustable dial on the water heater itself) then when it cools down it will fire up and reheat the water. it doesn't 'have' to run at night. you could turn it down to its lowest setting (which it'll still run) and save energy. but you will have to turn it up in the morning and wait for it to heat your water for your morning shower.
For food safety your refrigerator should run at 2 - 5 degrees C, so the water kept in it will be at that temperature.
the outlet pipe at the base of the shower has not got enough angel for the water to run free
More "VOLUME" flowing from the tub spout then the shower head as the shower head has a flow restrictor
Yes. The average temperature for a bath or shower is warmer than core body temperature. If a body is left in the tub for long periods of time, body temperature will begin to rise, just like anything else. Your body will react to maintain homeostasis, but its usually not enough to stop the rising temperature. Suggestion? Run a cooler bath, or add cold water if you are feeling too hot. If you are giving a bath to an infant, look at skin color, if the skin is really red, you should be lowering the temperature of the bath water. If you are wondering how hot a bath should be, run some water on the inside of your forearm, that is the most sensitive part of your arm. If its warm, its perfect :)
Cold air cannot hold as much moisture as warm air. If the dew point exceeds the air temperature, fog will form. You start off with a room at room temperature (about 20 - 25 C, about 70 F). As you run a shower that produces steam (rather than a cold shower), steam fills the room and condenses on the mirror, because the glass (being a good insulator) does not dissipate heat as quickly. Therefore, it remains at a cool temperature, and allows the water vapor to cool back to liquid water (fog).
Bad shower valve.
If you can get clean in 5 minutes that's all that counts. You should be able to take a 20 minute one before you run out of hot water. That's the only real time limit on the length of a shower.
If you have tub water-divertor or the head is clogged. Most likely former.
Many variables need to be supplied here. Size of water heater, Gallons per minute of shower head and volume of water being used. If the water heater is small, you only have 30 gallons of hot water available. If you have a 6 GPM shower head, that is only enough for about a 5 minute shower. If you have had the water heater checked out to make sure the heating element (if electric) isn't corroded or caked with calcium or making a lot of noise (boiling sounds) if it is gas, you can increase the temperature setting on the water heater. This will let you use more cold water and increase your shower duration. Changing your shower head to a low flow type will also increase you soak time. Another thing to consider is the distance of the shower from the water heater. If the pipes have to travel some distance in an uninsulated space, this will lower water temperature as it travels through the pipes. Hope this helped.
Run a new cold supply line from the source. This will drain less pressure from the the cold shower line.
Around 190-200 deg F.