Sleep vs XP

It's a comparison i make always daily, often XP is replaced by some other wowfactor like Badges of Justice, dkp, epics or just plain gaming fun... but the factor sleep is always part of that equation.
Our guild raids from 20h30 till 24h during weekdays normally and sundays we even start 30mins earlier. Our English friends join us on the raids but due to the timezone it's 19h30 till 23h for them.

Now let me sketch my situation here, however non-complex: i get up at 7h and try to arrive at work at 8h. Nine hours later at 17h i'm released from the clutches of the Raidleader at work and i head home. I cook/eat/feed the cats/whatever else is needed and then i often find myself in the virtual world of warcraft. 6 out of 7 days there is a raid available, 2 of those are optional but if you are one of the required classes there is quite some strong pressure.. mostly from myself in the form of guilth. Let's say we actually manage to stop at 12 (often we manage to pass that with 10-20mins, sometimes even a bit longer), this would mean i'm in bed within the next 10mins but then i often need a moment to settle after high pace action so i often see the clock reach 1 o' clock before passing out.
That adds up to 6 hours of sleep each night at the max, if i manage to wake up early or during the night i miss out even more.
I'd like to say this is the minimum ammount of sleep i need but truth said i'm on the edge here... around 12 my eyelids are growing quite heavy and i often have to fight against sleep to end the raid. Once i go past 12 o'clock the fight has gone too far and many times i start to develop a headache.
The next day i will be jawning constantly and if i really pushed it that headache will still be around to remind of yesterdays raid, the old gods only know why i don't have these use bags under my eyes after weeks of this abuse.

When i do manage to go to bed early for a change, i notice i'm more active during the day.. not much but still. So i am aware the effect staying up late has but still i'm not willing to give up on the fun. Gaming bad? Nonsence! Just staying up too late for it.
If i wouldn't have gamed online with other people it would have been easier to quit when i was tired but it's not so easy to abandon 9 other or even 24 other people. People you consider some sort of friends and who count on you. If i quit that can often ruin the raid, especially on the 10man runs and i'm playing the tank. I try to warn people in advance that 12h is my absolute endtime but when we manage to wipe on a boss due to a stupid reason at 11h56 you do know what is gonna happen: another try.
People do know whats the deal and ask me if i'm up for another run or that we should call it.... any idea what my answer on this normally is?
Eventho i told them hours in advance that 12h is the end for me i find myself torn once again, my bed is calling me and i can almost feel the fabric of my pillow on my face, yet the guilth is nagging again and then i hear myself say: "Okay, let's do a last shot then.. but i'm going after that!"
Luckily often this one extra attempt is all we need but what if we wipe again? It's up to me then to decide if we leave empty handed or not, do i want us to taddle off like sad little feldogs with their hanging tails between their langs?

This next sunday i won't log on.. not at all. Not in the morning, not in the afternoon and certainly not in the evening. I will use my time more effective for a change, do some long due chores, clean up in the house and most importantly: go to bed early!
I will be missing a raid because of this and i truelly hope i can be missed aswell as my GF who is going to be part of the package deal here, but i do feel a total non-wow day might do us some good. If this turns out as a noticeable positive thing i might make this a weekly event, perhaps try to attend the raid in the evening and take some other night off.. but lets see where this leads first.
I suppose an addicts first step towards getting better is admitting he's an addict, at least that point is behind me. ;)