I honestly think that if you're getting bored of Sc2, take a break. It really doesn't say anywhere you have to grind long gaming sessions, those don't really help you improve ( if you're playing them mindlessly that is.)
What does get me in the zone though is good ole Sc1 music :D. Or some of my music ( I listen to a variety, Metallica, Jimi Hendrix, Dre, Justice, and Daft Punk get me pumped though :D
For me there are two things that get me focused. If I loose a lot of games, going outside having a smoke and just relaxing a bit. If I win a lot of games unexpectedly losing a game really makes me focus on the next one.
If you find ways to force yourself to stay interested and keep playing you're going to burn out and be one of those guys posting about how he is bored of the game now in a few weeks. I play about 10 or less games a night and it's not time but quality that makes you better and 10 games is enough for a standard person.
Alcohol definitely helps, in small amounts of course. And isolation. Hearing people in the stairwell outside my apartment or people making noise in the common area or people... Basically isolate yourself from people.
Why try to play 10 consecutive games? Maybe take a break after 5 and make some food or something. If you take your mind off the game a bit and then hop back in you might find your concentration returning. O_o
You're actually going to need another 500 - 600 points to be able to play with the big boys.
I think everyone has their own way of getting into the zone. For me listening to the Zerg BGM keeps me focused oddly enough. Usually I like to listen to my own music, but I noticed that I make silly mistakes if I do that =P.
I have the same problem as you, when you starting going 10 + games you start feeling a bit of fatigue. That's because starcraft has such a strain on your mental state to play it. Typically I feel really really hot in my face after 10 - 12 games of SC2, forcing myself to play anymore usually amounts to bad stuff happening.
What I've been doing to give myself some rest is either watch a stream, watch a non-starcraft related video, or go over some replays. What I believe is best is either do something non-starcraft related for an hour or go over a few replays for an hour if you really want to improve yourself hardcore. Watching a replay can get you pumped up to play another set of 10 or so games, and after an hour of rest you should ready to play more.
But mass gaming for hours straight up seems too brutal for regular folks like us. I don't know how those Koreans can do it for years, its not a surprise they burn out, it's more of a surprise that they haven't burned out sooner.
A good night of sleep allows me to play up to 8 hours in a day with a few breaks in-between, unfortunately this doesn't happen often because I gotta wake up early in the morning for work.
And why would u need to be in the zone u play because it's fun just becuz ur diamond doesn't make u a pro.. Therefor u have no obligations to play and if you don't feel like then you shouldn't play the games aren't meant to be boring.