All paintings should never be in direct sunlight. This goes especially true for any paper art, watercolors, pastels, prints of artwork etc. A watercolor painting should have 99% UV protection glass at all times. All light sources emit harmful UV light rays. Sunlit and indoor lighting such as fluorescent and tungsten contain different amounts of UV energy that can cause irreversible damage to your artwork. Colors may fade, shift and become brittle. You can't avoid light completely, but never put a watercolor by a window that the sun will directly hit at certain times of the day. Even with the UV protection glass, just don't do it. Heat, pollution, moisture, poor quality framing materials all contribute to a damaged painting in time. When lighting your artwork is desirable use special low watt halogen-based bulbs that redirect damaging UV and infrared rays of light. That would be a good compromise.
When the work is respected this way, it can be passed down from one generation to another and still maintain most of its brilliance. Not only do you respect the artist that created it, you never know what a good conditioned piece of art will be worth in 5 to 10 or 15 years to come. Quite a few artist of the past were hardly known during their time painting and Van Gogh was one of them. But who knows how the evaluation of your art might turn out to be in years to come .If you watch the " Antiques Road Show" they're always showing paintings that grew in value over the years. Always consider in investing in good art because one day you might have the KINGS RANSOM! Most of my paintings are signed " R. Tino" but I then decided to sign them Ralph T. Tino. You'll start seeing that signature more and more as I continue to paint. Have a good day, week, year and so on and so forth.