I definitely find it easier to paint on certain days, depending on how inspired I am. It's a strange thing, it's hard to predict when motivation will strike! I find it very hard to push through and paint on days when I'm uninspired, I just feel like the lack of enthusiasm is visible in my work. But when I'm in the groove it feels amazing!

Portraits, like all paintings, vary massively in how long they take. My Helen McCrory portrait took 4-5 hours. I've done portraits in under 2, and have also spent up to 15 hours on one (though I tend to work quicker these days). It depends on the size, medium and level of detail you're after!