How much sleep is enough and necessary?

There are 2 school of thoughts regarding how much sleep is necessary:
1. Some says you need to have at least 6 to 7 hr sleep minimum or your productivity falls dramatically.
2. Other says sleep as less as possible, like 3 to 4 hrs hence you get more time awake to do things.

So which one to follow?

From my personal experience if I sleep less for few days I start to feel the lag in productivity and thinking clearly. But I can reset that feeling by sleeping more then usual for a day and then I become normal again.

Sleep is a very important component of onces life not only for mental health but physical too. Many athletes sleep 10 hrs a day so that their body can recover quickly from intense physical activities. Same is true for those working under stress.

So what do you do? I think it depends from person to person and how well do you sleep. Sometimes you sleep very less but you feel very fresh and sometimes its totally opposite, you sleep a lot and when you wake up us still feel you are tired. So It depends on your actual need. Try to get a good sleep for any hour you feel comfortable but make sure you get good sleep. To get good sleep follow this rules:
1. Make sure the room is dark so that you can fall a sleep soon.
2. Disengage for any digital devices (TV, mobiles etc) 30 min prior to your sleeping schedule. As they will make your brain active and it will be difficult to go to sleep.
3. Make sure there are no interruption while you are sleeping. No phone calls nothing should disturb your sleep.
4. Make sure the room temperature is cooler. This helps in getting better sleep.

So follow this rules and find out your sleeping cycle by testing how less can you sleep without feeling tired for the rest of the day. Do let me know your observations and as always any suggestion are welcome.