Or do you use fresh paint every time? Someone asked me that on my Facebook page and I thought it warranted a blog post :) . In general, I like to have freshly squeezed paint, especially for direct painting (as opposed to glazing, also known as working in layers). But it is not always practical to use fresh paint for every single painting session. So I compromise. I keep some paint in the palette wells but I don't fill them up completely (even though that usually makes the palette look better). I then add the colors I'm running out of before I paint. Or right in the middle of painting...that also happens.

So, why would you not want to just fill up the palette wells and not have to add more paint as often? Here are my reasons:

• Fresh paint is just that, fresh. It is ready to go the second you squeeze it out of the tube. It is pure, brilliant pigment uncontaminated by the neighboring color or that sneaky phtalo blue that just likes to invade the whole palette.
• Some watercolor paints tend to crumble when allowed to dry. It is possible to re-wet and reactivate them but they can become an annoyance when you have to deal with stray lumps of pigment right where you would want a nice uniform wash. Dropping some gum arabic into the pile of paint is supposed to help with that but I don't think it's worth the hassle.
• Digging dry paint out of the well requires you to rub it with your brush to "break it up", which can be damaging to the delicate brush hairs (do not do it with your kolinsky sable brush). This is how round brushes lose their points. One way to go around it is to use a stiffer, cheaper, synthetic brush for just that purpose - to re-activate dry paint. Once you have a nice puddle going, you can pick the paint up with your painting brush and paint.
• As I am moving towards larger work or working in series on several small paintings at the same time, I find it easier and faster to cover the surface with fresh paint rather than to try to pick up enough dried paint from the well. With Yupo, I often squeeze the paint directly onto the paper and then add water and mix it there.

Of course, there are some advantages to using dried-out paint:

• It is probably a little bit more economical. 
• I find that it suits better for plein air and for painting outside of my usual studio work. Fresh paint tends to run and leak in transport, while dried paint, even when re-activated, seems to be more stable and less messy. I usually refill my palette wells the night before I go. This also means you don't need to bring the tubes with you.
• If you work small, you may not need a lot of pigment at a time. Picking it up from the dried pile in the well will give you more control than a freshly squeezed blob of paint.
• Depending on how you use your paints, there may be not much difference at all between using it fresh or dry. Misting the dry paint with spray or mist bottle 15 minutes before you paint will soften the watercolors and make them ready to go.

Ultimately, it's what works for you. There is no right or wrong answer. How about you? Do you work with fresh paint exclusively or do you prefer to have a full palette of dried paint?