I'm sat here now, in front of my PC, on a night I had specifically put aside for painting, with my current project sat on my other desk, the paint mixture going dry. I had vowed to myself I was going to make progress tonight, yet I'm not doing.
The reason for this? My painting stamina has given up on me. I've realised, and I don't think i can be the only one, that my body can only take so much painting in one night. If this is an amount of time, or a certain amount of painting done, I don't yet know.
Perhaps how much you take depends on factors, such as tiredness, will to finish the model, etc etc. This evening I've been painting this wave serpent for my upcoming Eldar army:
This is exactly how the thing is still sat, the layer of highlighting, half finished(you'll notice the closer faring, nor the turret or the shield projectors are as light) in the other room. Before I put it down, my highlights were getting careless, fatter, not as neat, generally all over the place, as I realised I'd had enough.
I understand how much you can take in a sitting will vary from person to person(I know some peoples Hobby stamina runs out when their finger is removed from the spray can button), but treat this as a warning! Unless you want fat highlights on your curly tanks,
KNOW YOUR LIMITS!!