Machka, I think you are doing quite OK. I have given up on trying to replace chains before cassette wear causes new ones to skip; I am now in the mode of riding the drive train into the ground (until it skips unacceptably, that is). A colleage of mine has commuted more than 18 months 40km a day with very little maintanance to his chain other than pointing a can of WD-40 at his chain occasionally and I just replaced his first drivetrain for him. He got approx 12,000km. Some of the gears were extremely worn.

You deserve a new drive train and a medal.