Welcome to the forums. I was a lurker as well for many, many years, and I still tend to lurk the majority of the time.

Does it really shorten your lifespan? I would think that if you got very little sleep, you would be more likely to die in a car crash, so that would increase your risk of death, but the moment you change your lifestyle and start sleeping adequately again you would be fine. Not something I've ever gotten curious enough to research, but now I'm interested.

I suppose sleep should be a major concern for me, as I am on medication that is a major sedative (commonly abused for it). But on the other hand, I'm more of a night owl myself, so I like to stay up late, but am forced to wake up early for work, so I usually get only 6.5 hours of sleep (which isn't too bad), but then I'm often finding myself tired during the day. I know I need to get to bed earlier, but I haven't the discipline, as until now I've not known about any negative health problems it could be causing.

Edit: And it's 2 a.m.; I have to get up at 8 (maybe 8:30 if I sacrifice a leisurely morning for more sleep) to drive my wife to work, then take my daughter to a birthday party at Chuck E Cheese at noon. So at best I'm looking at 6.5 hours of sleep tonight if I fall asleep six minutes ago.

Thank you for welcoming me to the forums!

Without enough sleep, your brain doesn't have adequate time to flush itself with it's own version of lymphatic fluid. This process is essentially the brain "cleaning" itself whilst you sleep. The mental effects and consequences of < 6 hours of sleep are frightening to say the least.

Since you are getting 6-6.5 hours of sleep, I wouldn't be too concerned. What would be concerning is if you managed to achieve 7-8 hours of sleep, and still feel very tired during the day. EDS (Excessive daytime sleepiness) is a major indicator of respiratory issues (Hypopneas, Apneas) during sleep if you manage 7+ hours. 

Since you are on a sedative (depends on the sedative), your respiratory drive may be lessened. Sedatives can harm sleep in a large number of ways, although they may be necessary to achieve any sleep at all. People in the sleep community debate-to what degree they harm the sleep architecture. 

If you fear your sleep has been compromised, you might want to look into getting a referral for a sleep study. 

I sleep until i dont want to sleep

i run 100% on a 3-4 hrs

You may feel fine, or even "great" after 3-4 hours a day. The consequences of that amount can appear later in life. Although it is rare to feel 100% after 3-4 either way.

Alzheimer's and Dementia can pop up later. This is due to the build up of harmful proteins in your brain. The brain's "cleaning" process prevents the build up of these proteins.

If you can honestly get 3 hours of sleep every day and still feel "100%", then I am impressed. But it is unhealthy either way. 

I don't know. Since I was a young kid i have sleep bugger all hours. 30odd years later still the same lol.

Its not an every day thing, but it still has never bothered me,like ever. 

Hmm, I ask myself if the needed amount of sleeping time can be separated into chunks, so say 4 hours night sleep and 3 hours siesta in the afternoon? Or is a minimum time sleep needed in one go?

I need less than 6 hours.

Lately, I have reached a healthy balance. I'm cooking and reducing the amount of food I take, I only drink water (no tea, no coffee, no alcohol), I'm on a process of reducing the sugar now.
I'm doing sports at home, I'm going to sleep around midnight, and I wake up around 7. I feel great.

A few years ago, my work was tough, I was workaholic, I used to drink 2 bottle of vodka a week, ate too much... 

Got from 105 kg to now 87, I'm very happy, and I feel healthier than ever.

Do you drink 12 bottles of diet coke a day?